distributed database applications cosc 5050 week three

Distributed Database Applications

COSC 5050Week Three

Jiangping WangDistributed Database Applications

Outline

Cursors and data retrieval

Procedures

Functions

Parameters

Sequences


Cursors and Data Retrieval

PL/SQL integrates with the Oracle databaseSystem Global Area (SGA)Private working area for SQL statement

Cursor

To query data from the database and make that data available within PL/SQL programs

Implicit cursorExplicit cursorCursor variable


Cursor

Cursor is a pointer into a virtual table in the database

CURSOR employee_cur IS

SELECT fname, lname FROM employee;

OPEN employee_cur;

FETCH employee_cur INTO employee_rec;

CLOSE employee_cur;


Cursor Fetch Operation


Cursorcreate or replace procedure cursor_employee is CURSOR employee_cur IS SELECT fname, lname FROM employee WHERE ssn = '600000001'; employee_rec employee_cur%rowtype;begin OPEN employee_cur; FETCH employee_cur INTO employee_rec; dbms_output.put_line( employee_rec.fname || ' ' ||employee_rec.lname); CLOSE employee_cur;end;/


Cursor Attributes

Page 468%FOUND

Status of fetch operationTrue if fetch succeeded

%NOTFOUNDOpposite of %FOUND

%ROWCOUNTNumber of records fetched

%ISOPENTrue if the cursor is open

cursor_name%attribute_name


Referencing Variables in Cursor

Identifier precedence in a cursorQualifying variable with proc nameUsing standard naming conventions

create or replace PROCEDURE adjustIS l_code NUMBER := 1000; CURSOR double_code_cur IS SELECT code + l_code as adjusted FROM employee WHERE dept_num = 2; employee_rec double_code_cur%rowtype;begin OPEN double_code_cur; FETCH double_code_cur INTO employee_rec; dbms_output.put_line(employee_rec.adjusted); CLOSE double_code_cur; END;


Implicit CursorUse SELECT INTO

DECLARE l_department department.dept_name%TYPE;BEGIN SELECT dept_name INTO l_department FROM department WHERE dept_num = 1; DBMS_OUTPUT.PUT_LINE(l_department);END;

DECLARE l_department department%ROWTYPE;BEGIN SELECT * INTO l_department FROM department WHERE dept_num = 1; DBMS_OUTPUT.PUT_LINE(l_department.dept_name);END;


Implicit Cursor

DECLARE l_department department%ROWTYPE;BEGIN SELECT * INTO l_department FROM department WHERE dept_num = 3; DBMS_OUTPUT.PUT_LINE(l_department.dept_name);EXCEPTION WHEN NO_DATA_FOUND THEN DBMS_OUTPUT.PUT_LINE('No data!'); WHEN TOO_MANY_ROWS THEN DBMS_OUTPUT.PUT_LINE('Too many rows');END;/

Implicit SQL cursor attributes SQL%FOUNDSQL%NOTFOUNDSQL%ROWCOUNTSQL%ISOPEN

Error handlingWith exception


Explicit CursorExplicitly defined in declaration sectionComplete control over open, fetch, close

CURSOR company_cur IS SELECT company_id FROM company;

CURSOR name_cur (company_id_in IN NUMBER)IS SELECT name FROM company WHERE company_id = company_id_in;

CURSOR emp_cur RETURN employee%ROWTYPEIS SELECT * FROM employee WHERE department_id = 10;


Explicit Cursor

OpenFetchCloseExplicit cursor attributes

cursor%FOUNDcursor%NOTFOUNDcursor%ROWCOUNTcursor%ISOPEN


Explicit CursorDECLARE CURSOR c1 IS SELECT fname, lname, code, code*1.1 new_code FROM employee; rec c1%ROWTYPE;BEGIN OPEN c1; LOOP FETCH c1 INTO rec; EXIT WHEN c1%NOTFOUND; DBMS_OUTPUT.PUT_LINE( rec.fname || ' ' || rec.lname || ' ' || rec.code || ' ' || rec.new_code); END LOOP; CLOSE c1;END;/


Explicit CursorDECLARE l_dept_id NUMBER := 1; CURSOR name_cur (dept_id_in IN NUMBER) IS SELECT dept_name, lname FROM department inner join employee on department.dept_mgr_ssn = employee.ssn WHERE department.dept_num = dept_id_in; name_rec name_cur%ROWTYPE;BEGIN OPEN name_cur(l_dept_id); LOOP FETCH name_cur INTO name_rec; EXIT WHEN name_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE( name_rec.dept_name || ' ' || name_rec.lname); END LOOP; CLOSE name_cur;END;/


Explicit CursorDECLARE CURSOR emp_cur RETURN employee%rowtype IS SELECT * FROM employee WHERE dept_num = 15; emp_rec emp_cur%ROWTYPE;BEGIN OPEN emp_cur; LOOP FETCH emp_cur INTO emp_rec; EXIT WHEN emp_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE(emp_cur%rowcount || ': ' || emp_rec.fname || ' ' || emp_rec.lname); END LOOP; CLOSE emp_cur;END;/


Cursor Variable

Cursor variable points to or references an underlying cursor

DECLARE TYPE employee_curtype IS REF CURSOR RETURN employee%ROWTYPE; employee_curvar employee_curtype; employee_rec employee%ROWTYPE;BEGIN OPEN employee_curvar FOR SELECT * FROM employee; FETCH employee_curvar INTO employee_rec; CLOSE employee_curvar; dbms_output.put_line(employee_rec.fname);END;/


Cursor Loop

Cursor with simple loop

DECLARE CURSOR name_cur IS SELECT lname, fname FROM employee WHERE ssn like '8%'; name_rec name_cur%ROWTYPE;BEGIN OPEN name_cur; LOOP FETCH name_cur INTO name_rec; EXIT WHEN name_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE( name_rec.fname || ' ' || name_rec.lname); END LOOP; CLOSE name_cur;END;/


Cursor Loop

Cursor with simple loop

DECLARE CURSOR occupancy_cur IS SELECT pet_id, room_number FROM occupancy WHERE occupied_dt = TRUNC(SYSDATE); occupancy_rec occupancy_cur%ROWTYPE;BEGIN OPEN occupancy_cur; LOOP FETCH occupancy_cur INTO occupancy_rec; EXIT WHEN occupancy_cur%NOTFOUND; update_bill (occupancy_rec.pet_id, occupancy_rec.room_number); END LOOP; CLOSE occupancy_cur;END;


Cursor FOR Loop

Cursor For loop

DECLARE CURSOR occupancy_cur IS SELECT pet_id, room_number FROM occupancy WHERE occupied_dt = TRUNC(SYSDATE);BEGIN FOR occupancy_rec IN occupancy_cur LOOP update_bill (occupancy_rec.pet_id, occupancy_rec.room_number); END LOOP;END;


Cursor FOR Loop

Cursor FOR loop

DECLARE

CURSOR name_cur IS

SELECT lname, fname

FROM employee WHERE ssn like '8%';

BEGIN

FOR name_rec IN name_cur

LOOP

DBMS_OUTPUT.PUT_LINE(

name_rec.fname || ' ' || name_rec.lname);

END LOOP;

END;

/


Modular Code

PL/SQL offers the following structures that modularize your code in different ways

ProcedureFunctionTriggerPackage


Procedure

Procedure is a module that performs one or more actionsCan be a standalone call, executable statement


ProcedureCREATE OR REPLACEPROCEDURE get_happy (ename_in IN VARCHAR2)

Header

IS

hiredate DATE; Declarations

BEGIN

hiredate:= SYSDATE – 2; INSERT INTO employee (emp_name, hiredate)

VALUES (ename_in, hiredate);

Code Body

EXCEPTION * optional *

WHEN DUP_VAL_IN_INDEX THEN DBMS_OUTPUT.PUT_LINE (‘Cannot insert.’);

Exception block* optional *

END get_happy;

Jiangping Wang

Procedure



Procedureprocedure Add_employee (ssn in varchar2

, fname in varchar2, lname in varchar2, dept_num in number, code in number, sup_ssn in varchar2)

is begin

insert into employee values (ssn, fname, lname, dept_num, code,

sup_ssn);end;


Procedureprocedure delete_employee (tgt_ssn in varchar2)is cursor dept_mgr_cur (tst_ssn varchar2) is select dept_mgr_ssn from department where dept_mgr_ssn = tst_ssn; dept_mgr_cur_ssn varchar2(9);begin open dept_mgr_cur(tgt_ssn); fetch dept_mgr_cur into dept_mgr_cur_ssn; if (dept_mgr_cur%found) then update department set dept_mgr_ssn = NULL where dept_mgr_ssn = tgt_ssn; end if; delete from employee where ssn = tgt_ssn; close dept_mgr_cur;end;


Procedure

Calling a procedureProcedure is called as an executable PL/SQL statementCalled in a blockMust end with (;)

beginapply_discount( new_company_id, 0.15 );display_store_summary;display_store_summary();

end;


Function

Function is a module that returns a valueFunction can exist only as part of an executable statementFunction has a datatype


FunctionCREATE OR REPLACEFUNCTION soft_pillow (type_in IN VARCHAR2)

RETURN BOOLEAN

Header

IS

CURSOR pillow_cur (type_in pillow.pillow_type%TYPE) ISSELECT softnessFROM pillowWHERE pillow_type = type-in;

Pillow_rec pillow_cur%ROWTYPE;

Declarations

BEGIN

OPEN pillow_cur(type_in);FETCH pillow_cur INTO Pillow_rec;CLOSE pillow_cur;RETURN Pillow_rec.softness;

Code Body

EXCEPTION * optional *

Exception block* optional *

END soft_pillow;

Jiangping Wang

Function



Function

Defining function

create or replace function favorite_nickname( name_in in varchar2) return varchar2isbeginEnd;

Calling function

declarenickname varchar2(100) := favorite_nickname(‘Nic’);


Functioncreate or replace function get_department( ssn_in in employee.ssn%type) return department.dept_name%typeis l_dept_name department.dept_name%type;begin select dept_name into l_dept_name from department inner join employee on employee.dept_num = department.dept_num where ssn = ssn_in; dbms_output.put_line('department name: ' || l_dept_name); return l_dept_name;exception when no_data_found then dbms_output.put_line( 'no such employee or not in any department!'); return null;end;/


Parameter

Be used to pass information back and forthParameter declaration must be unconstrained

DECLARE company_name varchar2(60);

PROCEDURE display_company( company_name IN varchar2) IS …


Parameter ModeIN mode: Read-only

Is the default modeValue cannot be changedCan have default valuePassed by reference

OUT mode: Write-onlyHas no value until the endNo default valueActual parameter must be a variablePassed by value

IN OUT mode: Read-writeCannot have default valueMust be a variablePassed by value


Parametercreate or replace procedure delete_employee ( tgt_ssn_in in varchar2, removed_name_out out varchar2)is cursor dept_mgr_cur (tst_ssn varchar2) is select dept_mgr_ssn from department where dept_mgr_ssn = tst_ssn; dept_mgr_cur_ssn varchar2(9);begin open dept_mgr_cur(tgt_ssn_in); fetch dept_mgr_cur into dept_mgr_cur_ssn; if (dept_mgr_cur%found) then update department set dept_mgr_ssn = NULL where dept_mgr_ssn = tgt_ssn_in; end if; select lname into removed_name_out from employee where ssn = tgt_ssn_in; delete from employee where ssn = tgt_ssn_in; close dept_mgr_cur;end;/

Jiangping Wang

Parameter


create or replace PROCEDURE combine_and_format_names (first_name_inout IN OUT VARCHAR2, last_name_inout IN OUT VARCHAR2, full_name_out OUT VARCHAR2, name_format_in IN VARCHAR2 := 'LAST, FIRST')ISBEGIN first_name_inout := UPPER (first_name_inout); last_name_inout := UPPER (last_name_inout); IF name_format_in = 'LAST, FIRST' THEN full_name_out := last_name_inout || ', ' || first_name_inout; ELSIF name_format_in = 'FIRST LAST' THEN full_name_out := first_name_inout || ' ' || last_name_inout; END IF;END;/


Oracle SequencesIndependent object in the database

Not a data typeNot tied to a table or a columnCan be used anywhere a value is expected

Generate a numeric value that can be assigned to any column in any tableThe table attribute to which you assigned a value based on a sequence can be edited and modifiedCan be created and deleted anytime


Oracle SequencesCREATE SEQUENCE NAME [START WITH N] [INCREMENT BY N] [CACHE | NOCACHE]

CREATE SEQUENCE CUS_CODE_SEQ START WITH 20010 NOCACHE;CREATE SEQUENCE INV_NUMBER_SEQ START WITH 4010 NOCACHE;

SELECT * FROM USER_SEQUENCES;

DROP SEQUENCE CUS_CODE_SEQ;DROP SEQUENCE INV_NUMBER_SEQ;


Oracle SequencesINSERT INTO CUSTOMER VALUES (CUS_CODE_SEQ.NEXTVAL, ‘CONNERY’, ‘SEAN’, NULL, ‘615’, ‘898-2007’, 0.00);

INSERT INTO INVOICE VALUES (INV_NUMBER_SEQ.NEXTVAL, 20010, SYSDATE);

INSERT INTO LINE VALUES (INV_NUMBER_SEQ.CURRVAL, 1, ‘13-Q2/P2’, 1, 14.99);

INSERT INTO LINE VALUES (INV_NUMBER_SEQ.CURRVAL, 2, ‘23109-HB’, 1, 9.95);


Oracle SequencesOnce a sequence value is used (through NEXTVAL), it cannot be used againIf SQL statement rolls back, the sequence value does not roll backA sequence is not associated with a table

A sequence can be used to generate unique values for more than one tables

Dropping a sequence does not delete the values generatedA sequence has one purpose: assign unique numbers to stuff

Do not expect a sequence to return gap free values


HomeworkCreate a function that returns the next available customer ID. Create a stored procedure that accepts customer data as input arguments, adds a new customer record to the customer table.Create a stored procedure that accepts a numeric amount as an input argument that will be used as a filter threshold and prints a listing of customer information.Lab activities

distributed database applications cosc 5050 week three

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