0oracle sql scribe)

8/4/2019 0Oracle SQL Scribe)

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Oracle SQL Overview

1. Writing Basic SQL Statements2. Restricting and Sorting Data

3. Displaying Data from Multiple Tables

4. Manipulating Data:INSERT, UPDATE, DELETE

5. Creating and Managing Tables6. Creating Views


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1. Writing Basic

SQL Statements


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Capabilities of SQL SELECT

StatementsSelection Projection

Table 1 Table 2

Table 1 Table 1Join


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Basic SELECT Statement

SELECT [DISTINCT] {*, column [alias],...}

FROM table;

SELECT identifies whatcolumns.

FROM identifies whichtable.


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Writing SQL Statements

SQL statements are not case sensitive.

SQL statements can be on one ormore lines.

Keywords cannot be abbreviated orsplit across lines.

Clauses are usually placed on separate

lines. Tabs and indents are used to enhance

readability.


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Selecting All Columns

DEPTNO DNAME LOC--------- -------------- -------------

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

SQL> SELECT *

2 FROM dept;


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Selecting Specific Columns

DEPTNO LOC

--------- -------------

10 NEW YORK

20 DALLAS

30 CHICAGO

40 BOSTON

SQL> SELECT deptno, loc

2 FROM dept;


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Arithmetic Expressions

Create expressions on NUMBER and DATEdata by using arithmetic operators.

Operator

+

-

*

/

Description

Add

Subtract

Multiply

Divide


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Using Arithmetic Operators

SQL> SELECT ename, sal, sal+300

2 FROM emp;

ENAME SAL SAL+300

---------- --------- ---------KING 5000 5300

BLAKE 2850 3150

CLARK 2450 2750

JONES 2975 3275

MARTIN 1250 1550

ALLEN 1600 1900...

14 rows selected.


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Operator Precedence

Multiplication and division take priority

over addition and subtraction. Operators of the same priority are

evaluated from left to right.

Parentheses are used to forceprioritized evaluation and to clarifystatements.

* / + _


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Operator Precedence

SQL> SELECT ename, sal, 12*sal+100

2 FROM emp;

ENAME SAL 12*SAL+100

---------- --------- ----------KING 5000 60100

BLAKE 2850 34300

CLARK 2450 29500

JONES 2975 35800

MARTIN 1250 15100

ALLEN 1600 19300...

14 rows selected.


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Using Parentheses

SQL> SELECT ename, sal, 12*(sal+100)

2 FROM emp;

ENAME SAL 12*(SAL+100)

---------- --------- -----------KING 5000 61200

BLAKE 2850 35400

CLARK 2450 30600

JONES 2975 36900

MARTIN 1250 16200

...14 rows selected.


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Defining a Null Value

A null is a value that is unavailable,unassigned, unknown, or inapplicable.

A null is not the same as zero or a blankspace.

SQL> SELECT ename, job, comm2 FROM emp;

ENAME JOB COMM

---------- --------- ---------

KING PRESIDENT

BLAKE MANAGER

...

TURNER SALESMAN 0

...

14 rows selected.


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Null Values

in Arithmetic ExpressionsArithmetic expressions containing a nullvalue evaluate to null.

SQL> select ename, 12*sal+comm2 from emp

3 WHERE ename='KING';

ENAME 12*SAL+COMM---------- -----------

KING


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Defining a Column Alias

Renames a column heading

Is useful with calculations

Immediately follows column name;optional AS keyword between columnname and alias

Requires double quotation marks if it

contains spaces or special charactersor is case sensitive


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Using Column Aliases

SQL> SELECT ename AS name, sal salary2 FROM emp;

NAME SALARY

------------- ---------

...

SQL> SELECT ename "Name",

2 sal*12 "Annual Salary"

3 FROM emp;

Name Annual Salary

------------- -------------

...


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Concatenation Operator

Concatenates columns or characterstrings to other columns

Is represented by two vertical bars (||)

Creates a resultant column that is acharacter expression


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Using the Concatenation

OperatorSQL> SELECT ename||job AS "Employees"

2 FROM emp;

Employees-------------------

KINGPRESIDENT

BLAKEMANAGER

CLARKMANAGER

JONESMANAGER

MARTINSALESMANALLENSALESMAN

...

14 rows selected.


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Literal Character Strings

A literal is a character, expression, ornumber included in the SELECT list.

Date and character literal values mustbe enclosed within single quotationmarks.

Each character string is output once for

each row returned.


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Using Literal Character Strings

Employee Details-------------------------

KING is a PRESIDENT

BLAKE is a MANAGER

CLARK is a MANAGER

JONES is a MANAGER

MARTIN is a SALESMAN...

14 rows selected.

SQL> SELECT ename ||' '||'is a'||' '||job

2 AS "Employee Details"

3 FROM emp;


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Duplicate Rows

The default display of queries is all rows,including duplicate rows.

SQL> SELECT deptno

2 FROM emp;

DEPTNO

---------

10

30

1020

...

14 rows selected.


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Eliminating Duplicate Rows

Eliminate duplicate rows by using theDISTINCT keyword in the SELECT clause.

SQL> SELECT DISTINCT deptno

2 FROM emp;

DEPTNO

---------

10

20

30


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SQL and SQL*Plus Interaction

SQL*Plus

SQL Statements Buffer SQL Statements

Server

Query ResultsSQL*PlusCommands

Formatted Report


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SQL Statements Versus

SQL*Plus Commands

SQLstatements

SQL

A language

ANSI standard

Keyword cannot beabbreviated

Statements manipulatedata and tabledefinitions in thedatabase

SQL*Plus

An environment

Oracle proprietary

Keywords can beabbreviated

Commands do notallow manipulation ofvalues in the database

SQLbuffer

SQL*Pluscommands

SQL*Plusbuffer


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Log in to SQL*Plus. Describe the table structure.

Edit your SQL statement.

Execute SQL from SQL*Plus.

Save SQL statements to files andappend SQL statements to files.

Execute saved files. Load commands from file to buffer

to edit.

Overview of SQL*Plus


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Logging In to SQL*Plus

From Windows environment:

From command line:sqlplus [username[/password

[@database]]]


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Displaying Table Structure

Use the SQL*Plus DESCRIBE command todisplay the structure of a table.

DESC[RIBE] tablename


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Displaying Table Structure

SQL> DESCRIBE dept

Name Null? Type

----------------- -------- ------------

DEPTNO NOT NULL NUMBER(2)DNAME VARCHAR2(14)

LOC VARCHAR2(13)


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2. Restricting and Sorting Data


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Objectives

After completing this lesson, you shouldbe able to do the following:

Limit the rows retrieved by a query

Sort the rows retrieved by a query


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Limiting Rows Using a Selection

"retrieve allemployees

in department 10"

EMP

EMPNO ENAME JOB ... DEPTNO

7839 KING PRESIDENT 107698 BLAKE MANAGER 307782 CLARK MANAGER 107566 JONES MANAGER 20...

EMP


7839 KING PRESIDENT 107782 CLARK MANAGER 107934 MILLER CLERK 10


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Limiting Rows Selected

Restrict the rows returned by using theWHERE clause.

The WHERE clause follows the FROM

clause.

SELECT [DISTINCT] {*| column [alias], ...}

FROM table[WHERE condition(s)];


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Using the WHERE Clause

SQL> SELECT ename, job, deptno

2 FROM emp

3 WHERE job='CLERK';

ENAME JOB DEPTNO

---------- --------- ---------

JAMES CLERK 30

SMITH CLERK 20

ADAMS CLERK 20

MILLER CLERK 10


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Character Strings and Dates

Character strings and date values areenclosed in single quotation marks.

Character values are case sensitive and

date values are format sensitive. The default date format is DD-MON-YY.

SQL> SELECT ename, job, deptno

2 FROM emp3 WHERE ename = 'JAMES';


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Comparison Operators

Operator

=

>

>=

SELECT ename, sal, comm

2 FROM emp

3 WHERE sal


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Other Comparison Operators

Operator

BETWEEN

...AND...

IN(list)

LIKE

IS NULL

Meaning

Between two values (inclusive)

Match any of a list of values

Match a character pattern

Is a null value


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Using the BETWEEN Operator

ENAME SAL

---------- ---------

MARTIN 1250

TURNER 1500

WARD 1250ADAMS 1100

MILLER 1300

SQL> SELECT ename, sal

2 FROM emp

3 WHERE sal BETWEEN 1000 AND 1500;

Lowerlimit

Higherlimit

Use the BETWEEN operator to displayrows based on a range of values.


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Using the IN Operator

Use the IN operator to test for values in alist.

SQL> SELECT empno, ename, sal, mgr

2 FROM emp3 WHERE mgr IN (7902, 7566, 7788);

EMPNO ENAME SAL MGR

--------- ---------- --------- ---------

7902 FORD 3000 75667369 SMITH 800 7902

7788 SCOTT 3000 7566

7876 ADAMS 1100 7788


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Using the LIKE Operator

Use the LIKE operator to performwildcard searches of valid search stringvalues.

Search conditions can contain either

literal characters or numbers. % denotes zero or many characters.

_ denotes one character.

SQL> SELECT ename

2 FROM emp

3 WHERE ename LIKE 'S%';


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Using the LIKE Operator

You can combine pattern-matchingcharacters.

You can use the ESCAPE identifier tosearch for "%" or "_".

SQL> SELECT ename

2 FROM emp3 WHERE ename LIKE '_A%';

ENAME

----------

MARTIN

JAMES

WARD


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Using the IS NULL Operator

Test for null values with the IS NULLoperator.

SQL> SELECT ename, mgr2 FROM emp

3 WHERE mgr IS NULL;

ENAME MGR

---------- ---------KING


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Logical Operators

Operator

AND

OR

NOT

Meaning

Returns TRUE if bothcomponent

conditions are TRUE

Returns TRUE if eithercomponent

condition is TRUE

Returns TRUE if the following

condition is FALSE


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Using the AND Operator

AND requires both conditions to be TRUE.

SQL> SELECT empno, ename, job, sal

2 FROM emp

3 WHERE sal>=1100

4 AND job='CLERK';

EMPNO ENAME JOB SAL

--------- ---------- --------- ---------

7876 ADAMS CLERK 1100

7934 MILLER CLERK 1300


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Using the OR Operator

OR requires either condition to be TRUE.SQL> SELECT empno, ename, job, sal

2 FROM emp

3 WHERE sal>=1100

4 OR job='CLERK';

EMPNO ENAME JOB SAL--------- ---------- --------- ---------

7839 KING PRESIDENT 5000

7698 BLAKE MANAGER 2850

7782 CLARK MANAGER 2450

7566 JONES MANAGER 2975

7654 MARTIN SALESMAN 1250...

7900 JAMES CLERK 950

...

14 rows selected.


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Using the NOT Operator

SQL> SELECT ename, job

2 FROM emp

3 WHERE job NOT IN ('CLERK','MANAGER','ANALYST');

ENAME JOB

---------- ---------

KING PRESIDENT

MARTIN SALESMAN

ALLEN SALESMAN

TURNER SALESMANWARD SALESMAN


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Rules of Precedence

Override rules of precedence by usingparentheses.

Order Evaluated Operator

1 All comparisonoperators

2 NOT3 AND

4 OR


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Rules of Precedence

ENAME JOB SAL

---------- --------- ---------

KING PRESIDENT 5000

MARTIN SALESMAN 1250

ALLEN SALESMAN 1600TURNER SALESMAN 1500

WARD SALESMAN 1250

SQL> SELECT ename, job, sal2 FROM emp

3 WHERE job='SALESMAN'

4 OR job='PRESIDENT'

5 AND sal>1500;


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Rules of Precedence

ENAME JOB SAL

---------- --------- ---------

KING PRESIDENT 5000

ALLEN SALESMAN 1600

Use parentheses to force priority.SQL> SELECT ename, job, sal

2 FROM emp

3 WHERE (job='SALESMAN'

4 OR job='PRESIDENT')

5 AND sal>1500;


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ORDER BY Clause Sort rows with the ORDER BY clause

ASC: ascending order, default DESC: descending order

The ORDER BY clause comes last in theSELECT statement.

SQL> SELECT ename, job, deptno, hiredate

2 FROM emp

3 ORDER BY hiredate;

ENAME JOB DEPTNO HIREDATE

---------- --------- --------- ---------SMITH CLERK 20 17-DEC-80

ALLEN SALESMAN 30 20-FEB-81

...

14 rows selected.


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Sorting in Descending Order

SQL> SELECT ename, job, deptno, hiredate2 FROM emp

3 ORDER BY hiredate DESC;

ENAME JOB DEPTNO HIREDATE

---------- --------- --------- ---------ADAMS CLERK 20 12-JAN-83

SCOTT ANALYST 20 09-DEC-82

MILLER CLERK 10 23-JAN-82

JAMES CLERK 30 03-DEC-81

FORD ANALYST 20 03-DEC-81

KING PRESIDENT 10 17-NOV-81MARTIN SALESMAN 30 28-SEP-81

...

14 rows selected.


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Sorting by Column Alias

SQL> SELECT empno, ename, sal*12 annsal2 FROM emp

3 ORDER BY annsal;

EMPNO ENAME ANNSAL

--------- ---------- ---------7369 SMITH 9600

7900 JAMES 11400

7876 ADAMS 13200

7654 MARTIN 15000

7521 WARD 15000

7934 MILLER 15600

7844 TURNER 18000

...

14 rows selected.


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Sorting by Multiple Columns The order of ORDER BY list is the order of

sort.

You can sort by a column that is not in theSELECT list.

SQL> SELECT ename, deptno, sal

2 FROM emp

3 ORDER BY deptno, sal DESC;

ENAME DEPTNO SAL

---------- --------- ---------

KING 10 5000

CLARK 10 2450

MILLER 10 1300

FORD 20 3000...

14 rows selected.


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Summary

SELECT [DISTINCT] {*| column [alias], ...}

FROM table

[WHERE condition(s)]

[ORDER BY {column, expr, alias} [ASC|DESC]];


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3. Displaying Datafrom Multiple Tables


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Objectives


Write SELECT statements to access

data from more than one table usingequality and nonequality joins

View data that generally does not meet

a join condition by using outer joins Join a table to itself


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EMPNO DEPTNO LOC----- ------- --------7839 10 NEW YORK7698 30 CHICAGO

7782 10 NEW YORK7566 20 DALLAS7654 30 CHICAGO7499 30 CHICAGO...14 rows selected.

Obtaining Data from Multiple TablesEMP DEPT

EMPNO ENAME ... DEPTNO------ ----- ... ------7839 KING ... 107698 BLAKE ... 30...7934 MILLER ... 10

DEPTNO DNAME LOC------ ---------- --------

10 ACCOUNTING NEW YORK20 RESEARCH DALLAS30 SALES CHICAGO40 OPERATIONS BOSTON


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What Is a Join?

Use a join to query data from more thanone table.

Write the join condition in the WHEREclause.

Prefix the column name with the tablename when the same column nameappears in more than one table.

SELECT table1.column, table2.column

FROM table1, table2

WHERE table1.column1 = table2.column2;


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Cartesian Product

A Cartesian product is formed when:

A join condition is omitted

A join condition is invalid All rows in the first table are joined to

all rows in the second table

To avoid a Cartesian product, alwaysinclude a valid join condition in aWHERE clause.


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Generating a Cartesian Product

ENAME DNAME------ ----------KING ACCOUNTINGBLAKE ACCOUNTING

...KING RESEARCHBLAKE RESEARCH...56 rows selected.

EMP (14 rows) DEPT (4 rows)

EMPNO ENAME ... DEPTNO------ ----- ... ------7839 KING ... 107698 BLAKE ... 30...7934 MILLER ... 10

DEPTNO DNAME LOC------ ---------- --------10 ACCOUNTING NEW YORK20 RESEARCH DALLAS30 SALES CHICAGO40 OPERATIONS BOSTON

Cartesian

product:14*4=56 rows


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Types of Joins

Equijoin Non-equijoin Outer join Self join


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What Is an Equijoin?EMP DEPT

EMPNO ENAME DEPTNO------ ------- -------7839 KING 107698 BLAKE 307782 CLARK 107566 JONES 20

7654 MARTIN 307499 ALLEN 307844 TURNER 307900 JAMES 307521 WARD 307902 FORD 20

7369 SMITH 20...14 rows selected.

DEPTNO DNAME LOC------- ---------- --------

10 ACCOUNTING NEW YORK30 SALES CHICAGO10 ACCOUNTING NEW YORK20 RESEARCH DALLAS

30 SALES CHICAGO30 SALES CHICAGO30 SALES CHICAGO30 SALES CHICAGO30 SALES CHICAGO20 RESEARCH DALLAS

20 RESEARCH DALLAS...14 rows selected.

Foreign key Primary key


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Retrieving Recordswith Equijoins

SQL> SELECT emp.empno, emp.ename, emp.deptno,

2 dept.deptno, dept.loc

3 FROM emp, dept

4 WHERE emp.deptno=dept.deptno;

EMPNO ENAME DEPTNO DEPTNO LOC

----- ------ ------ ------ ---------

7839 KING 10 10 NEW YORK

7698 BLAKE 30 30 CHICAGO

7782 CLARK 10 10 NEW YORK

7566 JONES 20 20 DALLAS

...

14 rows selected.


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Qualifying AmbiguousColumn Names

Use table prefixes to qualify columnnames that are in multiple tables.

Improve performance by using table

prefixes.

Distinguish columns that have identicalnames but reside in different tables by

using column aliases.


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Additional Search ConditionsUsing the AND Operator

EMP DEPT

EMPNO ENAME DEPTNO------ ------- -------7839 KING 107698 BLAKE 30

7782 CLARK 107566 JONES 207654 MARTIN 307499 ALLEN 307844 TURNER 307900 JAMES 30

7521 WARD 307902 FORD 207369 SMITH 20


DEPTNO DNAME LOC------ --------- --------

10 ACCOUNTING NEW YORK30 SALES CHICAGO

10 ACCOUNTING NEW YORK20 RESEARCH DALLAS30 SALES CHICAGO30 SALES CHICAGO30 SALES CHICAGO30 SALES CHICAGO

30 SALES CHICAGO20 RESEARCH DALLAS20 RESEARCH DALLAS



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Using Table Aliases

Simplify queries by using table aliases.SQL> SELECT emp.empno, emp.ename, emp.deptno,

2 dept.deptno, dept.loc

3 FROM emp, dept

4 WHERE emp.deptno=dept.deptno;

SQL> SELECT e.empno, e.ename, e.deptno,

2 d.deptno, d.loc

3 FROM emp e, dept d

4 WHERE e.deptno=d.deptno;


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Joining More Than Two Tables

NAME CUSTID----------- ------JOCKSPORTS 100TKB SPORT SHOP 101VOLLYRITE 102JUST TENNIS 103

K+T SPORTS 105SHAPE UP 106WOMENS SPORTS 107... ...9 rows selected.

CUSTOMER

CUSTID ORDID------- -------

101 610102 611104 612106 601

102 602106 604106 605


ORD

ORDID ITEMID------ -------

610 3611 1612 1601 1602 1


ITEM


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Non-Equijoins

EMP SALGRADE

salary in the EMP

table is between

low salary and high

salary in the SALGRADE

table

EMPNO ENAME SAL------ ------- ------7839 KING 50007698 BLAKE 28507782 CLARK 2450

7566 JONES 29757654 MARTIN 12507499 ALLEN 16007844 TURNER 15007900 JAMES 950


GRADE LOSAL HISAL----- ----- ------1 700 12002 1201 14003 1401 2000

4 2001 30005 3001 9999


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Retrieving Recordswith Non-Equijoins

ENAME SAL GRADE

---------- --------- ---------

JAMES 950 1

SMITH 800 1

ADAMS 1100 1

...

14 rows selected.

SQL> SELECT e.ename, e.sal, s.grade

2 FROM emp e, salgrade s

3 WHERE e.sal

4 BETWEEN s.losal AND s.hisal;


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Outer Joins

EMP DEPT

No employee in the

OPERATIONS department

ENAME DEPTNO----- ------KING 10BLAKE 30CLARK 10JONES 20...

DEPTNO DNAME------ ----------10 ACCOUNTING30 SALES10 ACCOUNTING

20 RESEARCH...40 OPERATIONS


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Outer Joins

You use an outer join to also see rowsthat do not usually meet the joincondition.

Outer join operator is the plus sign (+).


FROM table1, table2

WHERE table1.column(+)= table2.column;


FROM table1, table2

WHERE table1.column = table2.column(+);


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Using Outer Joins

SQL> SELECT e.ename, d.deptno, d.dname2 FROM emp e, dept d

3 WHERE e.deptno(+) = d.deptno

4 ORDER BY e.deptno;

ENAME DEPTNO DNAME

---------- --------- -------------

KING 10 ACCOUNTING

CLARK 10 ACCOUNTING

...

40 OPERATIONS15 rows selected.


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Self Joins

EMP (WORKER) EMP (MANAGER)

MGR in the WORKER table is equal to EMPNO in the

MANAGER table

EMPNO ENAME MGR----- ------ ----7839 KING7698 BLAKE 78397782 CLARK 7839

7566 JONES 78397654 MARTIN 76987499 ALLEN 7698

EMPNO ENAME----- --------

7839 KING7839 KING

7839 KING7698 BLAKE7698 BLAKE


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Joining a Table to Itself

WORKER.ENAME||'WORKSFOR'||MANAG-------------------------------

BLAKE works for KING

CLARK works for KING

JONES works for KING

MARTIN works for BLAKE


SQL> SELECT worker.ename||' works for '||manager.ename2 FROM emp worker, emp manager

3 WHERE worker.mgr = manager.empno;


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Summary

Equijoin Non-equijoin Outer join Self join


FROM table1, table2

WHERE table1.column1 = table2.column2;


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4. Manipulating Data:INSERT, UPDATE, DELETE


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Data Manipulation Language

A DML statement is executed when you:

Add new rows to a table

Modify existing rows in a table

Remove existing rows from a table

A transactionconsists of a collection ofDML statements that form a logical unit

of work.


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Adding a New Row to a Table

DEPT

DEPTNO DNAME LOC

------ ---------- --------10 ACCOUNTING NEW YORK20 RESEARCH DALLAS30 SALES CHICAGO40 OPERATIONS BOSTON

New row

50 DEVELOPMENT DETROIT

DEPT

DEPTNO DNAME LOC------ ---------- --------

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS30 SALES CHICAGO40 OPERATIONS BOSTON

insert a new row

into DEPT table

50 DEVELOPMENT DETROIT


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The INSERT Statement

Add new rows to a table by using theINSERT statement.

Only one row is inserted at a time with

this syntax.

INSERT INTO table [(column [, column...])]

VALUES (value [, value...]);

I i N R


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Inserting New Rows

Insert a new row containing values foreach column.

List values in the default order of the

columns in the table. Optionally list the columns in the

INSERT clause.

Enclose character and date valueswithin single quotation marks.

SQL> INSERT INTO dept (deptno, dname, loc)

2 VALUES (50, 'DEVELOPMENT', 'DETROIT');1 row created.

I i R i h N ll V l


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Inserting Rows with Null Values

Implicit method: Omit the column fromthe column list.

SQL> INSERT INTO dept (deptno, dname )

2 VALUES (60, 'MIS');

1 row created.

Explicit method: Specify the NULLkeyword.

SQL> INSERT INTO dept2 VALUES (70, 'FINANCE', NULL);

1 row created.

C i R


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Copying Rowsfrom Another Table

Write your INSERT statement with asubquery.

Do not use the VALUES clause.

Match the number of columns in theINSERT clause to those in the subquery.

SQL> INSERT INTO managers(id, name, salary, hiredate)

2 SELECT empno, ename, sal, hiredate3 FROM emp

4 WHERE job = 'MANAGER';

3 rows created.

Ch i D t i T bl


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Changing Data in a TableEMP

update a row

in EMP table

EMP


7839 KING PRESIDENT 107698 BLAKE MANAGER 307782 CLARK MANAGER 107566 JONES MANAGER 20...

20


7839 KING PRESIDENT 107698 BLAKE MANAGER 307782 CLARK MANAGER 107566 JONES MANAGER 20

...

Th UPDATE St t t


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The UPDATE Statement

Modify existing rows with the UPDATEstatement.

Update more than one row at a time, ifrequired.

UPDATE table

SETcolumn

=value

[,column

=value, ...

][WHERE condition];

U d ti R i T bl


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Updating Rows in a Table

Specific row or rows are modified whenyou specify the WHERE clause.

All rows in the table are modified if youomit the WHERE clause.

SQL> UPDATE emp

2 SET deptno = 20

3 WHERE empno = 7782;1 row updated.

SQL> UPDATE employee

2 SET deptno = 20;

14 rows updated.

U d ti R B d


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Updating Rows Basedon Another Table

Use subqueries in UPDATE statements toupdate rows in a table based on valuesfrom another table.

SQL> UPDATE employee2 SET deptno = (SELECT deptno

3 FROM emp

4 WHERE empno = 7788)

5 WHERE job = (SELECT job

6 FROM emp

7 WHERE empno = 7788);2 rows updated.

R i R f T bl


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delete a row

from DEPT table

Removing a Row from a TableDEPT

DEPTNO DNAME LOC------ ---------- --------10 ACCOUNTING NEW YORK20 RESEARCH DALLAS30 SALES CHICAGO40 OPERATIONS BOSTON50 DEVELOPMENTDETROIT60 MIS...

DEPT

DEPTNO DNAME LOC------ ---------- --------

10 ACCOUNTING NEW YORK20 RESEARCH DALLAS

30 SALES CHICAGO40 OPERATIONS BOSTON60 MIS...

Th DELETE St t t


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The DELETE Statement

You can remove existing rows from atable by using the DELETE statement.

DELETE [FROM] table

[WHERE condition];

D l ti R f T bl


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Specific rows are deleted when youspecify the WHERE clause.

All rows in the table are deleted if youomit the WHERE clause.

Deleting Rows from a Table

SQL> DELETE FROM department

2 WHERE dname = 'DEVELOPMENT';

1 row deleted.

SQL> DELETE FROM department;

4 rows deleted.

Database Transactions


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Database Transactions

Consist of one of the followingstatements:

DML statements that make up one

consistent change to the data One DDL statement

One DCL statement

Committing Data


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Committing Data

SQL> UPDATE emp

2 SET deptno = 10

3 WHERE empno = 7782;

1 row updated.

Make the changes.

Commit the changes.SQL> COMMIT;

Commit complete.

Read Consistency


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Read Consistency

Read consistency guarantees aconsistent view of the data at all times.

Changes made by one user do notconflict with changes made by anotheruser.

Read consistency ensures that on thesame data:

Readers do not wait for writers Writers do not wait for readers

Implementation of Read


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Implementation of ReadConsistency

UPDATE emp

SET sal = 2000

WHERE ename ='SCOTT';

Datablocks

Rollbacksegments

changedandunchangeddata

beforechangeold data

User A

User B

Readconsistentimage

SELECT *

FROM emp;

Locking


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Locking

Oracle locks:

Prevent destructive interaction betweenconcurrent transactions

Require no user action

Automatically use the lowest level ofrestrictiveness

Are held for the duration of thetransaction

Have two basic modes: Exclusive Share

Summary


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Summary

Description

Adds a new row to the table

Modifies existing rows in the table

Removes existing rows from the table

Makes all pending changes permanent

Allows a rollback to the savepoint marker

Discards all pending data changes

Statement

INSERT

UPDATE

DELETE

COMMIT

SAVEPOINT

ROLLBACK


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5. Creating and ManagingTables

Database Objects


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118

Database Objects

Object Description

Table Basic unit of storage; composed of rows

and columns

View Logically represents subsets of data from

one or more tables

Sequence Generates primary key values

Index Improves the performance of some queries

Synonym Gives alternative names to objects

Naming Conventions


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Naming Conventions

Must begin with a letter

Can be 130 characters long

Must contain only AZ, az, 09, _, $,and #

Must not duplicate the name of anotherobject owned by the same user

Must not be an Oracle Server reservedword

The CREATE TABLE Statement


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The CREATE TABLE Statement

You must have : CREATE TABLE privilege

A storage area

You specify:

Table name Column name, column datatype, and

column size

CREATE TABLE [schema.]table(columndatatype [DEFAULT expr][, ...]);

Referencing Another Users


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Referencing Another User s

Tables

Tables belonging to other users are notin the users schema.

You should use the owners name as aprefix to the table.

Creating Tables


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Creating Tables

SQL> CREATE TABLE dept2 (deptno NUMBER(2),

3 dname VARCHAR2(14),

4 loc VARCHAR2(13));

Table created.

Create the table.

Confirm table creation.SQL> DESCRIBE dept

Name Null? Type

--------------------------- -------- ---------

DEPTNO NUMBER(2)

DNAME VARCHAR2(14)

LOC VARCHAR2(13)

Datatypes


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yp

Datatype Description

VARCHAR2(size) Variable-length character data

CHAR(size) Fixed-length character data

NUMBER(p,s) Variable-length numeric data

DATE Date and time values

LONG Variable-length character dataup to 2 gigabytes

CLOB Single-byte character data up to 4gigabytes

RAW and LONG RAW Raw binary data

BLOB Binary data up to 4 gigabytes

BFILE Binary data stored in an externalfile; up to 4 gigabytes

The ALTER TABLE Statement


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The ALTER TABLE Statement

Use the ALTER TABLE statement to:

Add a new column

Modify an existing column

Define a default value for the new columnALTER TABLE table

ADD (column datatype [DEFAULT expr]

[, column datatype]...);

ALTER TABLE tableMODIFY (column datatype [DEFAULT expr]

[, column datatype]...);

Adding a Column


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Adding a ColumnDEPT30

EMPNO ENAME ANNSAL HIREDATE------ ---------- --------7698 BLAKE 34200 01-MAY-817654 MARTIN 15000 28-SEP-817499 ALLEN 19200 20-FEB-817844 TURNER 18000 08-SEP-81

...

add anewcolumnintoDEPT30table

DEPT30

EMPNO ENAME ANNSAL HIREDATE------ ---------- --------7698 BLAKE 34200 01-MAY-817654 MARTIN 15000 28-SEP-817499 ALLEN 19200 20-FEB-817844 TURNER 18000 08-SEP-81

...

JOB

JOB

New column

Adding a Column


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Adding a Column

You use the ADD clause to add columns.

EMPNO ENAME ANNSAL HIREDATE JOB

--------- ---------- --------- --------- ----

7698 BLAKE 34200 01-MAY-81

7654 MARTIN 15000 28-SEP-81

7499 ALLEN 19200 20-FEB-817844 TURNER 18000 08-SEP-81

...

6 rows selected.

SQL> ALTER TABLE dept30

2 ADD (job VARCHAR2(9));

Table altered.

The new column becomes the last column.

Modifying a Column


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Modifying a Column

You can change a columns datatype,size, and default value.

A change to the default value affectsonly subsequent insertions to the table.

ALTER TABLE dept30

MODIFY (ename VARCHAR2(15));

Table altered.

Dropping a Table


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Dropping a Table

All data and structure in the table isdeleted.

Any pending transactions are

committed. All indexes are dropped.

You cannotroll back this statement.

SQL> DROP TABLE dept30;

Table dropped.

Changing the Name of an Object


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Changing the Name of an Object

To change the name of a table, view,sequence, or synonym, you execute theRENAME statement.

You must be the owner of the object.

SQL> RENAME dept TO department;Table renamed.

Summary


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137

Summary

Statement Description

CREATE TABLE Creates a table

ALTER TABLE Modifies table structures

DROP TABLE Removes the rows and table structure

RENAME Changes the name of a table, view,sequence, or synonym

TRUNCATE Removes all rows from a table andreleases the storage space

COMMENT Adds comments to a table or view


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6. Creating Views

Objectives


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139

Objectives


Describe a view

Create a view

Retrieve data through a view

Alter the definition of a view

Insert, update, and delete data througha view

Drop a view

Database Objects


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Database Objects

Description

Basic unit of storage; composed of rows

and columns

Logically represents subsets of data from

one or more tables

Generates primary key values

Improves the performance of some queries

Alternative name for an object

Object

Table

View

Sequence

Index

Synonym

What Is a View?


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141

What Is a View?

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO----- ------- --------- ----- --------- ----- ----- -------

7839 KING PRESIDENT 17-NOV-81 5000 10

7698 BLAKE MANAGER 7839 01-MAY-81 2850 30

7782 CLARK MANAGER 7839 09-JUN-81 2450 10

7566 JONES MANAGER 7839 02-APR-81 2975 20

7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30

7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30

7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30

7900 JAMES CLERK 7698 03-DEC-81 950 30

7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30

7902 FORD ANALYST 7566 03-DEC-81 3000 20

7369 SMITH CLERK 7902 17-DEC-80 800 20

7788 SCOTT ANALYST 7566 09-DEC-82 3000 20

7876 ADAMS CLERK 7788 12-JAN-83 1100 20

7934 MILLER CLERK 7782 23-JAN-82 1300 10

EMP Table

EMPNO ENAME JOB MGR HIREDATE SAL COMMDEPTNO

----- -------- --------- ---- --------- ------ ----- ------

-

7839 KING PRESIDENT 17-NOV-81 5000

10

7782 CLARK MANAGER 7839 09-JUN-81 1500 300

10

7934 MILLER CLERK 7782 23-JAN-82 1300

10

7566 JONES MANAGER 7839 02-APR-81 2975

20

7788 SCOTT ANALYST 7566 09-DEC-82 3000

20

7876 ADAMS CLERK 7788 12-JAN-83 1100

20

7369 SMITH CLERK 7902 17-DEC-80 800

20

7902 FORD ANALYST 7566 03-DEC-81 3000

20

7698 BLAKE MANAGER 7839 01-MAY-81 2850

EMPNO ENAME JOB------ -------- -----------

7839 KING PRESIDENT

7782 CLARK MANAGER

7934 MILLER CLERK

EMPVU10 View

Why Use Views?


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Why Use Views?

To restrict database access

To make complex queries easy

To allow data independence

To present different views of the samedata

Simple Views


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Simple Viewsand Complex Views

Feature Simple Views Complex Views

Number of tables One One or more

Contain functions No YesContain groups of data No Yes

DML through view Yes Not always

Creating a View


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144

Creating a View

You embed a subquery within theCREATE VIEW statement.

The subquery can contain complexSELECT syntax.

The subquery cannot contain anORDER BY clause.

CREATE [OR REPLACE] [FORCE|NOFORCE] VIEWview

[(alias[, alias]...)]

AS subquery

[WITH CHECK OPTION [CONSTRAINTconstraint

]][WITH READ ONLY]

Creating a View


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Creating a View

Create a view, EMPVU10, that containsdetails of employees in department 10.

Describe the structure of the view byusing the SQL*Plus DESCRIBE

command.SQL> DESCRIBE empvu10

SQL> CREATE VIEW empvu10

2 AS SELECT empno, ename, job

3 FROM emp

4 WHERE deptno = 10;View created.

Creating a View


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146

Creating a View

Create a view by using column aliasesin the subquery.

Select the columns from this view bythe given alias names.

SQL> CREATE VIEW salvu30

2 AS SELECT empno EMPLOYEE_NUMBER, ename NAME,

3 sal SALARY

4 FROM emp5 WHERE deptno = 30;

View created.

Retrieving Data from a View


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147

et e g ata o a e

EMPLOYEE_NUMBER NAME SALARY

--------------- ---------- ---------

7698 BLAKE 2850

7654 MARTIN 1250

7499 ALLEN 1600

7844 TURNER 1500

7900 JAMES 950

7521 WARD 1250

6 rows selected.

SQL> SELECT *2 FROM salvu30;

Querying a View


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148

Q y g

USER_VIEWS

EMPVU10SELECT empno, ename, jobFROM empWHERE deptno = 10;

SQL*Plus

SELECT *FROM empvu10;

EMP7839 KING PRESIDENT7782 CLARK MANAGER7934 MILLER CLERK

Modifying a View


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149

y g

Modify the EMPVU10 view by using

CREATE OR REPLACE VIEW clause. Addan alias for each column name.

Column aliases in the CREATE VIEWclause are listed in the same order as thecolumns in the subquery.

SQL> CREATE OR REPLACE VIEW empvu10

2 (employee_number, employee_name, job_title)

3 AS SELECT empno, ename, job4 FROM emp

5 WHERE deptno = 10;

View created.

Creating a Complex View


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150

g p

Create a complex view that contains groupfunctions to display values from two tables.

SQL> CREATE VIEW dept_sum_vu

2 (name, minsal, maxsal, avgsal)

3 AS SELECT d.dname, MIN(e.sal), MAX(e.sal),

4 AVG(e.sal)5 FROM emp e, dept d

6 WHERE e.deptno = d.deptno

7 GROUP BY d.dname;

View created.

Rules for Performing


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gDML Operations on a View

You can perform DML operations onsimple views.

You cannot remove a row if the view

contains the following: Group functions

A GROUP BY clause

The DISTINCT keyword

Rules for PerformingDML Operations on a View


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152

DML Operations on a View

You cannot modify data in a view if it contains: Any of the conditions mentioned in the

previous slide

Columns defined by expressions

The ROWNUM pseudocolumn

You cannot add data if:

The view contains any of the conditions

mentioned above or in the previous slide There are NOT NULL columns in the base

tables that are not selected by the view

Using the WITH CHECK OPTION


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153

gClause

You can ensure that DML on the view stayswithin the domain of the view by using theWITH CHECK OPTION clause.

Any attempt to change the departmentnumber for any row in the view will failbecause it violates the WITH CHECK OPTIONconstraint.


2 AS SELECT *

3 FROM emp4 WHERE deptno = 20

5 WITH CHECK OPTION CONSTRAINT empvu20_ck;

View created.

Denying DML Operations


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154

y g p

You can ensure that no DML operationsoccur by adding the WITH READ ONLYoption to your view definition.


2 (employee_number, employee_name, job_title)

3 AS SELECT empno, ename, job4 FROM emp

5 WHERE deptno = 10

6 WITH READ ONLY;

View created.

Any attempt to perform a DML on anyrow in the view will result in OracleServer error.

Removing a View


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g

Remove a view without losing databecause a view is based on underlyingtables in the database.

SQL> DROP VIEW empvu10;

View dropped.

DROP VIEWview;

Summary


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y

A view is derived from data in other

tables or other views.

A view provides the followingadvantages:

Restricts database access Simplifies queries

Provides data independence

Allows multiple views of the same data Can be dropped without removing the

0oracle sql scribe)

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