its232 introduction to database management systems

ITS232Introduction To Database Management Systems

Siti Nurbaya Ismail

Faculty of Computer Science & Mathematics,

Universiti Teknologi MARA (UiTM), Kedah

| A2-3039 | ext:2561 | [email protected] | 012-7760562 |

CHAPTER 7An Introduction To SQL

Part 2: DDL & DML

Objectives

To be able to apply SQL command. How to use DML in SQL

2 major components:1. Data Definition Language (DDL)

defining database structure. allows database objects such as schemas, domains,

tables, views and indexes to be created and destroyed.

2. Data Manipulation Language (DML) retrieving and updating data. used to populate and query the tables. data manipulation.

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Data Defination Language (DDL)Defining database structure/schema

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Chapter 7: An Introduction To SQL7.3 Data Definition Languages (DDL)

Data Definition SQL commands describe the database structure

or schema:COMMAND/OPTION

DESCRIPTION

CRATE SCHEMA AUTHORIZATION

Creates a new database schema

CREATE TABLE Create a new table in the user’s database schema

NOT NULL Constraints that ensures that a column doesn’t

have a null valueUNIQUE Constraints that ensures that a column

doesn’t have a duplicate values

ALTER TABLE Modify a table definition

DROP TABLE Permanently delete a table and its structure

Chapter 7: An Introduction To SQL7.3 Data Definition Languages (DDL): Create Table

printerNO desc color staffNO

Create table ‘printer’ with printerNo as a primary key and staffNo as a foreign

key;Staff(staffNO,staffNAME,city,postcode)Printer(printerNO, desc, color, staffNO*)

CREATE TABLE printer(printerNO VARCHAR(5) NOT NULL PRIMARY KEY, desc VARCHAR(16), color VARCHAR(8), FOREIGN KEY (staffNO) REFERENCES staff(staffNO));

An empty table ‘printer’ is created with printerNO as primary key and staffNO as a foreign key:

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Chapter 7: An Introduction To SQL7.3 Data Definition Languages (DDL): Alter Table

ALTER command is used if there is a change on the table’s attribute.

The following SQL statement will add an attribute to table ‘staff’.ALTER TABLE staffADD telno char(11);

The following SQL statement will rename the column color in table ‘printer’.ALTER TABLE printer

RENAME COLUMN color TO printerColor;

The following SQL statement will change the width of desc’s colum to 25 digits in table ‘printer’.ALTER TABLE printerMODIFY (desc VARCHAR(25));

Chapter 7: An Introduction To SQL7.3 Data Definition Languages (DDL): In Brief

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SQL Statement

Descriptions

CREATE TABLE Create a new table- Primary Key

*NOT NULL:: a column does not have a null value

*UNIQUE :: a column does not have duplicate value- Foreign Key, attributes, data types of attributes, length of attributes

DROP TABLE Delete table and its structure-RESTRICT :: table with FK will not be deleted-CASCADE :: all attribute will be deleted

ALTER TABLE Change table attribute-ADD :: add table attribute-RENAME COLUMN :: rename an attribute -MODIFY ::modify attribute structure

Data Manipulation Language (DML)Manipulate data

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Data Manipulation Language(DML)

Data Manipulation in SQL is an ability for manipulating the data to provide information needs

by users.

Manipulating the data referees to process of:selecting the datado some operation at the datauser view it or save it in the database

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SELECT * FROM printerWHERE color = ‘red’ OR color = ‘blue’;

DML: Queries: SELECT Statement

SELECT Statement• The SELECT statement allows you to find, retrieve, and display

data.

• To execute the SELECT statement on a table, you must be the table owner, have DBA or SYSADM security privileges, or have the SELECT privilege for that table.

• The result of SELECT statement is a set of rows known as the result set, which meets the conditions specified in the SELECT statement

SQL SELECT Syntax

NoteSQL is not case sensitive { SELECT is the same as select }

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SELECT column_name(s)FROM table_name;

SELECT *FROM table_name;

DML: Queries: SELECT Statement

printerNO description color price

P123 Dot-matrix Red 249.56

HP874 Laser Jet Blue 559.99

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Select all data from table printer.

Select printerNO and price from table printer.

SELECT *FROM printer;

SELECT printerNO, priceFROM printer;

printerNO

price

P123 249.56

HP874 559.99

DML: Queries: SELECT DISTINCT Statement

SELECT DISTINCT Statement• In a table, some of the columns may contain duplicate

values. • The DISTINCT keyword can be used to return only distinct

(different) values.

SQL SELECT DISTINCT Syntax

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SELECT DISTINCT column_name(s)FROM table_name;

DML: Queries: SELECT DISTINCT Statement

The following statement only will select the distinct values from the column named city from table staff.

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SELECT DISTINCT cityFROM staff;

staffNO staffNAME city

ABC987 Nadz Kuala Lumpur

ABC988 Aina Jerantut

ABC999 Halimaton Jerantut

city

Kuala Lumpur

Jerantut

SQL LIKE Operator

The LIKE operator is used in a WHERE statement to search for a specified pattern in a column.

SQL LIKE Syntax

Note

The LIKE operator is commonly used with SQL Wildcards

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SELECT column_name(s)FROM table_nameWHERE column_name LIKE patern;

SQL LIKE Operator



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SELECT *FROM staffWHERE city LIKE “K%”;

The following select staffs living in a city start with “K” from table ‘staff’.

SQL Wildcards

• SQL wildcards can be used when searching for data in a database.• SQL wildcards can substitute for one or more characters when

searching for data in a database.• SQL wildcards must be used with the SQL LIKE operator.• With SQL, the following wildcards can be used:

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Wildcard Description

% A substitute for zero or more characters

_ A substitute for exactly one character

[charlist] Any single character in charlist

[^charlist] or[!charlist]

Any single character not in charlist

Wildcards: Using The % Wildcard

Select staff living in the city that start with ‘La’ from staff table.

Select staff living in the city that contain pattern ‘wi’ from staff table.

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SELECT *FROM staffWHERE city LIKE "La%";

SELECT *FROM staffWHERE city LIKE "%wi%";

Wildcards: Using The _ Wildcard

Select staff with a name that starts with any character, followed by ‘da’ from staff table.

Select staff with a name that starts with "S", followed by any character, followed by "ar", followed by any character, followed by "s" from staff table.

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SELECT *FROM staffWHERE staffNANE LIKE "_da";

SELECT *FROM staffWHERE staffNANE LIKE "S_ar_s";

Wildcards: Using The [charlist] Wildcard

Select staff with a name that starts with "a" or "s" or "p" from staff table.

Select staff name that do not starts with “"a" or "s" or "p" from staff table.

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SELECT *FROM staffWHERE staffNANE LIKE "[asp]%";

SELECT *FROM staffWHERE staffNANE LIKE "[!asp]%";

DML: Data Entry

The INSERT INTO command inserts new rows into a table.

When you insert data into a child table that has a foreign key linking it to a parent table, you must obey referential integrity rules.

This means you cannot insert a value into a child key that does not exist in the parent key unless it is a NULL value.

You must insert a new row into the parent key first.

To insert a string that contains a single quote, you must replace the single quote in the string with two consecutive single quotes.

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DML: Data Entry

SQL INSERT INTO Syntax• It is possible to write the INSERT INTO statement in two forms. • The first form doesn't specify the column names where the data will

be inserted, only their values:

• The second form specifies both the column names and the values to be inserted:

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INSERT INTO table_nameVALUES (value1, value2,…);

INSERT INTO table_name (column1,column2,…)VALUES (value1, value2,…);

DML: Data Entry


ABC123 Norain Ipoh

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The following insert values into table ‘staff’.

INSERT INTO staff VALUES (‘ABC123’, ‘Norain', ‘Ipoh’);

DML: Deleting Table Rows

The DELETE command deletes all rows matching the search condition from a table.

You can only delete rows from a single table, and you cannot delete rows from the system tables.

To execute the DELETE command, you must be the table owner, have delete privilege on the table, or have DBA or SYSADM security privileges.

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SQL DELETE Syntax

Note

Notice the WHERE clause in the DELETE syntax. The WHERE clause

specifies which record or records that should be deleted. If you omit the

WHERE clause, all records will be deleted!

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DELETE FROM table_nameWHERE some column=some value


DELETE record as specified in WHERE clause.

The following example deletes all staff whose name begins with “Nisa" from the staff table.

The following example deletes staff number ABC125 from the staff table.

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DELETE FROM staffWHERE staffNO=“ABC123” AND city=“Ipoh”;

DELETE FROM staffWHERE staffNAME LIKE “Nisa%”;

DELETE FROM staffWHERE staffNO =“ABC125”;

DML: Making Changes to Data Items

The UPDATE command updates existing rows in a table.

When you update a column, the new column values must satisfy the column constraints and referential integrity.

If the column has a DEFAULT value defined, you can use the DEFAULT keyword to set the value of the column to the default value.

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SQL UPDATE Syntax

Note

Notice the WHERE clause in the UPDATE syntax. The WHERE clause specifies which record or records that should be updated. If you omit the WHERE clause, all records will be updated!

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UPDATE table_nameSET column1=value,column2=value2,…WHERE some column=some value


• Shows how to update the staff table and change the city value for staff named “Rosliza".

• Shows how to give a salary raise of 5% to staff named “Wafiy".

•Update description for printer with printerNO F380.

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UPDATE staffSET city=“Bangi”WHERE staffNAME = “Rosliza”;

UPDATE staffSET salary=salary*1.05WHERE staffNAME = “Wafiy”;

UPDATE printerSET description=“KO”WHERE printerNO = “F380”;

DML: COMMIT

The COMMIT statement terminates the current transaction and makes all

changes under the transaction persistent.

COMMIT is used for saving the data that has been changed permanently because whenever you perform any DML like UPDATE, INSERT or DELETE then you are required to write COMMIT at the end of all or every DML operation in order to save it permanently.

If you do not write COMMIT and you program crashes then your data will be restored into its previous condition.

The COMMIT statement has the following general format:

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UPDATE printer SET indate = ‘15/01/2007' WHERE printerNO = 'F380'; COMMIT;

DML: ROLLBACK

The ROLLBACK statement terminates the current transaction and cancel all changes made under the transaction.

ROLLBACK is used if you want to restore your data into its previous condition.

ROLLBACK can be write at any time after the DML queries has been written but remember once COMMIT has been written then you cannot rollback the data.

You can only rollback the DML queries that have been written after the last commit statement.

The ROLLBACK statement has the following general format:

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INSERT INTO staffVALUES (“ABC990”, “Shafiza”, “Johor”)

ROLLBACK;

DML: COMMIT & ROLLBACK

The concept of COMMIT and ROLLBACK is designed for data consistency

because many uses manipulate data of the same table, using the same database so the user must get updated data. That is why COMMIT and ROLLBACK are used for.

COMMIT to save whatever has been done. It is used to permanently store it in memory.

ROLLBACKto undo something. If we use roll-back, the particular changes made are undone.

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DML: Compound Statement with SELECT

Symbol

Meaning

= Equal to

< Less than

<= Less than or equal to

> Greater than

>= Greater than or equal to

<> Not equal to*

*Some SQL version use != 32

– ANDto combine two search conditions which must be both true.

– ORto combine two search conditions when one or the other (or both) must be true

You can combine simple conditions with the logical operators

AND, OR, and NOT to form compound conditions.


Select only the staff live in Merbok AND age greater then or equal to 40 years old from table staff.

Select only the staff live in Penang OR age greater then or equal to 40 years old from table staff.

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SELECT *FROM staffWHERE city=“Merbok” AND age >= 40;

SELECT *FROM staffWHERE city=“Penang” AND age >= 40;


Select only the staff live in Merbok OR Penang AND age greater then or equal to 40 years old from table staff.

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SELECT *FROM staffWHERE (city=“Merbok” OR city=“Penang”) AND age >= 40;

Example

Delete all biscuits with chocolate flavor from tblbiscuit.

Delete all order from customerC001 that have status cancel from tblorder.

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tblcustomer(custNO, custNAME, custEMAIL)tblbiscuit(bisNO, bisNAME, bisFLAVOUR, bisPRICE)tblorder(orderNO,*custNO,*bisNO, orderadate, qty, status)

Example

Change all status to confirm for biscuit BIS101 for customer C135.

Increase biscuit price 10% for biscuit with strawberry flavor.

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Example

List down all customer name and email who order biscuit cornflakes.

List down all biscuit details being order by customer C010.

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SQL Alias

• You can give a table or a column another name by using an alias. This can be a good thing to do if you have very long or complex table names or column names.

• An alias name could be anything, but usually it is short.• Usually it is used in multiple table joint.

SQL Alias Syntax For Tables

SQL Alias Syntax For Columns

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SELECT column_name(s)FROM table_nameAS alias_name

SELECT column_name AS alias_nameFROM table_name

SQL Alias

The following statement list all the staff name that work at IT department.

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staffNO staffNAME

city salary

departNO


2300 0001

ABC988 Aina Jerantut 2500 0002

ABC989 Halimaton Jerantut 2200 0001

ABC990 Norain Johor 2000 0003

departNO departNAME

0001 IT

0002 Network

0003 Management

staff department

SELECT s.staffNAMEFROM staff AS s, department AS dWHERE (d.departNO=s.departNO) AND d.departNAME=“IT”;

staffNAME

Nadz

Halimaton

SQL JOINs

• The JOIN keyword is used in an SQL statement to query data from two or more tables, based on a relationship between certain columns in these tables.

• Tables in a database are often related to each other with keys.

• A primary key is a column (or a combination of columns) with a unique value for each row. Each primary key value must be unique within the table. The purpose is to bind data together, across tables, without repeating all of the data in every table.

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SQL JOINs

Different SQL JOINs

• JOIN / INNER JOINReturn rows when there is at least one match in both tables

• LEFT JOINReturn all rows from the left table, even if there are no matches in the right table

• RIGHT JOINReturn all rows from the right table, even if there are no matches in the left table

• FULL JOINReturn rows when there is a match in one of the tables

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SQL INNER JOIN

SQL INNER JOIN Syntax

NOTE

INNER JOIN is the same as JOIN.

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SELECT column_name(s)FROM table_name1INNER JOIN table_name2ON table_name1.column_name = table_name2.column_name

SQL INNER JOIN

The following statement list all the staff name that work at IT department.

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staffNO staffNAME

city salary

departNO


2300 0001

ABC988 Aina Jerantut 2500 0002

ABC989 Halimaton Jerantut 2200 0001

ABC990 Norain Johor 2000 0003

departNO departNAME

0001 IT

0002 Network

0003 Management

staff department

SELECT staff.staffNAME,depart.departNAMEFROM staffINNER JOIN departmentON department.departNO=staff.departNO;

staffNAME

Nadz

Halimaton

DML: Two-Table Joins

Besides INNER JOIN, you can also use the following statements to combines two tables with join conditions.

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staff(staffNO, staffNAME, city, salary, departmentNO*)department(departNO, departNAME)

SELECT s.staffNAMEFROM staff AS s, department AS dWHERE (d.departNO=s.departNO) AND d.departNAME=“IT”;

SELECT staff.staffNAME,department.departNAMEFROM staffINNER JOIN departmentON department.departNO=staff.departNO;

DML: Multiple-Table Joins

A multiple table join is a join of more than two tables with join conditions for pairs of table. – A join condition is a comparison (relational operators) on two columns from

each table.

Following is a three table joins which selects all the customer name that order biscuit Tart Nenas Gunting.

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customer(custNO, custNAME, custEMAIL)biscuit(bisNO, bisNAME, bisFLAVOUR, bisPRICE)order(orderNO,*custNO,*bisNO, orderadate, qty, status)

SELECT custNAMEFROM customer AS c, biscuit AS b, order AS o WHERE c.custNO=o.custNO AND o.bisNO=b.bisNO AND b.bisNAME=“Tart Nenas Gunting“;

DML: Multiple-Table Joins

List down all customer name, biscuit name and order quantity that customer had order with confirm status.

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DML: GROUP BY Statement

GROUP BY statement– produce summary data within a group.

a group is a set of rows that have the same values of group by columns.

a single row of aggregate results is produced for each group. the column you want to group results by is identified by its column

name.

– restrict what you can enter in the SELECT statement. – SELECT statement in GROUP BY statement must be one of the

following: An aggregate function, which produces a single value summarizing the rows in

the group. A grouping column which is listed in the GROUP BY statement. A constant. An expression involving a combination of the above. 47


SQL GROUP BY Syntax

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SELECT column_name(s), aggregate_function(column_name)FROM table_nameGROUP BY column_name;


The following statement will output staff average salary group by city.

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staffNO staffNAME city salary gender departNO

ABC987 Nadz Kuala Lumpur 2300 Male 0001

ABC988 Aina Jerantut 2500 Female 0002

ABC989 Halimaton Jerantut 2200 Female 0001

ABC990 Norain Johor 2000 Female 0003

staff

SELECT city, MIN(salary) AS minSALARYFROM staffGROUP BY city;

city minSALARY

Kuala Lumpur

2300

Jerantut 2200

Johor 2000

DML: ORDER BY Keyword

The ORDER BY keyword • is used to sort the result-set by a specified column.• sort the records in ascending order by default.• By default the records are in ascending order or you can used ASC

keyword • If you want to sort the records in a descending order, you can use DESC

keyword.• The default order is ascending. NULL values are treated as larger that

non-null values for sorting purposes.

SQL ORDER BY Syntax

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SELECT column_name(s)FROM table_nameORDER BY column_name(s) ASC|DESC

DML: ORDER BY Keyword

The following statement will output staff average salary group by city.

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staffNO staffNAME

city salary

gender departNO


2300 Male 0001

ABC988 Aina Jerantut 2500 Female 0002

ABC989 Halimaton Jerantut 2200 Female 0001

ABC990 Norain Johor 2000 Female 0003

staff

SELECT city, MIN(salary) AS minSALARYFROM staffGROUP BY cityORDER BY city DESC;

city minSALARY

Jerantut 2200

Johor 2000

Kuala Lumpur

2300

DML: HAVING Statement

HAVING statement is used to select or reject a group.

The following example shows the average salary for staff based on city where the total staff salary exceeds RM 2000.

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staffNO staffNAME

city salary gender

departNO


2300 Male 0001

ABC988 Aina Jerantut 2500 Female

0002

ABC989 Halimaton Jerantut 2200 Female

0001

ABC990 Norain Johor 2000 Female

0003

SELECT city, AVG(salary) AS avgSALARYFROM staffGROUP BY cityHAVING SUM(salary)> 2000 ;

city avgSALARY

Kuala Lumpur

2300

Jerantut 2350

SQL Aggregate Functions

SQL aggregate functions return a single value, calculated from values in a column

COUNT( ) returns the number of rows

SUM( ) returns the sum

AVG( ) returns the average value

MIN( ) returns the smallest value

MAX( ) returns the largest value

FIRST( ) returns the first value

LAST( ) returns the last value

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SQL Aggregate Functions

Each operates on a single column of a table and returns a single value.

COUNT, MIN, and MAX apply to numeric and non-numeric fields

SUM and AVG may be used on numeric fields only.

Apart from COUNT(*), each function eliminates nulls first and operates only on remaining non-null values.

COUNT(*) counts all rows of a table, regardless of whether nulls or duplicate values occur.

Can use DISTINCT before column name to eliminate duplicates.

DISTINCT has no effect with MIN/MAX, but may have with SUM/AVG.

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MIN/MAX/AVG

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penNO descr color qty

1001 Xtra-Fine Red 12

1002 Fine Blue 32

1003 Medium Pink 4

pen

SELECT MIN(qty)AS minQTY, MAX(qty) AS maxQTY, AVG(qty) AS avgQTYFROM pen;

minQTY maxQTY avgQTY

4 32 16

SUM/COUNT

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1002 Fine Blue 32

1003 Medium Pink 4

pen

SELECT SUM(qty)AS totalQTYFROM pen;

totalQTY

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SELECT COUNT(penNO)AS penNUMBERFROM pen;

penNUMBER

3

FIRST/LAST

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1002 Fine Blue 32

1003 Medium Pink 4

pen

SELECT FIRST(color)AS firstCOLORFROM pen;

firstCOLOR

Red

SELECT LAST(color)AS lastCOLORFROM pen;

lastCOLOR

Pink

Example

a. Find biscuit name that have the highest price.

b. List down all the biscuit order quantity for each biscuit type.

c. List down all the biscuit order quantity for each customer and sort according to the customer name.

d. List down how many customer order being made for each biscuit.

e. List down all customer name and email who order more then 5 biscuits.

f. List down biscuit information that never being order yet.58


Find biscuit name that have the highest price.

SELECT bisNAMEFROM tblbiscuitWHERE bisPRICE = (SELECT MAX(bisPRICE)

FROM tblbiscuit);

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its232 introduction to database management systems

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