Procedures and Cursors

8/13/2019 Procedures and Cursors

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PL/SQL programmingProcedures and Cursors

Lecture 4 [Part 2]


2/24

SQL refresher Basic commands

SELECT, !SE"T, #ELETE, $P#%TE

%&'a(s remem)er to state the ta)&e*s+ (ou

are se&ecting data from

oin ta)&es )( primar( and foreign -e(s

.i&ter data using 0E"E c&ause

SELECT 111 ."3 111 [0E"E 111]


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SQL scripts Set of commands to run in seuence1 Stored as a te5t fi&e *e1g1 using !otepad+ on a dis-

and not in the data dictionar(1 t is accessed )( fi&e

name

E5ecuted using 6 or Start1

Script called:Create_lecturer_copy.sql

Executed by:

SQL> @create_lecturer_copy.sql


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The SQL Procedure B&oc- of SQL statements stored in the #ata dictionar(

and ca&&ed )( app&ications

Satisfies freuent&(7used or critica& app&ication &ogic hen ca&&ed a&& code 'ithin the procedure is e5ecuted

*un&i-e pac-ages+ %ction ta-es p&ace on ser8er not c&ient #oes not return 8a&ue to ca&&ing program !ot a8ai&a)&e in rac&e 9 or o&der %ids securit( as #B% ma( grant access to procedures not

ta)&es, therefore some users cannot access ta)&es e5ceptthrough a procedure


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Bui&ding a procedure: contents;1 Create or rep&ace command

21 )


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;1 Create or rep&ace

command21 )


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Compi&ing and e5ecuting

procedures Li-e an( program the code needs to )e compi&ed1

6inf&ation@rise compi&es the procedure in a fi&e 'ith this name ma-es it a8ai&a)&e to the data)ase

E5ecute inf&ation@rise e5ecutes the procedure1

"emem)er to compi&e a procedure again once ithas )een amended1

.or ease of use, it is )est to 'rite procedures in

notepadand then run them, this means that the(

can )e easi&( edited and (ou ha8e a )ac-up cop(


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E5amp&eCREATE OR REPLACE PROCEDUREvalidate_customer (v_cust VARCHAR)

AS

v_count NUMBER;

BEGIN

SELEC C!UN(") INTOv_count

#R!M CUS!MER

$HERE CUS_C!%E & v_cust;

IF v_count > 0 THEN

%BMS_!U'U'U_LNE(*customer valid+);

ELSE

%BMS_!U'U'U_LNE(*customer not reco,nised+);

END IF;

END;

%n( 8aria)&espassed into

procedure

Loca& 8aria)&es

used )( procedure

SQL


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Cursors in SQL Ena)&es users to &oop round a se&ection of

data1

Stores data se&ect from a uer( in a temp

area for use 'hen opened1

$se comp&e5 actions 'hich 'ou&d not )e

feasi)&e in standard SQL se&ection ueries


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% #E3A #ata has )een se&ected from the emp&o(ee ta)&e1

This data needs to )e amended in the fo&&o'ing

'a(: Each mem)er of staff is to )e increased one grade1

Each mem)er of staff is to ha8e a > pa( rise1

f the pa( rise does not ta-e them to the min for theirne' grade the( are to )e increased to the min for thatgrade

f the pa( rise mo8es them a)o8e the ma5 for a gradethe( are to )e increased to the ma5 on&(1


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S(nta5 for Cursors #ec&ared as a 8aria)&e in the same 'a( as

standard 8aria)&es

dentified as cursor t(pe

SQL inc&uded

E1g1Cursor cur_emp is

Select emp_id, surname name, grade,

salary

From employee

Where regrade is true;


12/24

Cursors % cursor is a temp store of data1

The data is popu&ated 'hen the cursor is opened1

nce opened the data must )e mo8ed from the

temp area to a &oca& 8aria)&e to )e used )( the

program1 These 8aria)&es must )e popu&ated in the

same order that the data is he&d in the cursor1 The data is &ooped round ti&& an e5it c&ause is

reached1


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Actie setActie set

Current ro!Current ro!Cursor

"#$% S&'() C*+-

"$$ /01+S &A1A2+""33 SC0(( A1A*4S(

"3"$ A5A&S C*+-

"%67 F05 A1A*4S(

Cursor unctionsCursor unctions


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Controllin! CursorControllin! Cursor

Create aCreate anamednamed

S8* areaS8* area

5+C*A+5+C*A+5+C*A+5+C*A+

'denti9y'denti9ythe actiethe actie

setset

0:+10:+10:+10:+1

*oad the*oad thecurrentcurrent

ro! intoro! into

arialesariales

F+(C)F+(C)F+(C)F+(C)

(est 9or(est 9ore


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Controllin! Cursor*Controllin! Cursor*0pen the cursor.0pen the cursor.

CursorCursor

:ointer:ointer

Fetch a ro! 9rom the cursor.Fetch a ro! 9rom the cursor.

CursorCursor

:ointer:ointer

Continue until empty.Continue until empty.

CursorCursor

:ointer:ointer

Close the cursor.Close the cursor.

CursorCursor


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Cursor +ttributesCursor +ttributes

Attriute (ype 5escription

>'S0:+1 ?oolean +aluates to (+ i9 the cursor

is open

>10(F015 ?oolean +aluates to (+ i9 the most

recent 9etch does not return a ro!

>F015 ?oolean +aluates to (+ i9 the most

recent 9etch returns a ro!;complement o9 >10(F015

>0WC01( 1umer +aluates to the total numer o9

ro!s returned so 9ar

)tain status information a)out a cursor1


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Create or replace procedure proc_test as

v_empid number;

Cursor cur_sample is

Select empid from employee

where grade > 4;

Begin

open cur_sample;

loop

fetch cur_sample into v_empid;

exit when cur_samplenotfound;

update employeeset salary ! salary " #$$

where empid ! v_empid;

end loop;

%nd;

&pen cursor for use'

(oops round each value

returned by the cursor

)lace the value from thecursor into the variable

v_empid

Stop when

no morerecords

are found

*#4+,

-**4#

##./,

-*#*4

./#4,

0ata

returnedby cursor

,eclare

Cursor


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!otepad fi&e ca&&ed:

Create_procedures.sql

;+ pen SQLDP&us and &ogon

2+ %t the prompt enter:

-create_procedures

ou 'i&& get a prompt 'hich shou&d sa( Fprocedure createdG

=+ To run the procedure enter:

Execute proc_test

4+ f (ou chec- (our data (ou shou&d no' find that the procedure has run successfu&&(


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$se of conditions f statements can )e used

1f 2condition> 3hen

''

%nd if; E5amp&e

"emem)er to end the if statement and use of indented code'i&& ma-e it easier to de)ugA

. . .

IF v_enae ! "#ILLER" THEN

v_$o% &! "SALES#AN";

v_'e(tno &! )*; v_ne+_co &! ,a- 0./0;

END IF;

. . .

. . .

IF v_enae ! "#ILLER" THEN

v_$o% &! "SALES#AN";

v_'e(tno &! )*; v_ne+_co &! ,a- 0./0;

END IF;

. . .


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The HSPE! %ttri)ute .etch ro's on&( 'hen the cursor is open1

$se the HSPE! cursor attri)ute )efore

performing a fetch to test 'hether the cursor isopen1

E5amp&e

IF NOT cu_,a(-e1ISOPEN THEN

OPEN cu_,a(-e;

END IF;

LOOP

FETCH cu_,a(-e...

IF NOT cu_,a(-e1ISOPEN THEN

OPEN cu_,a(-e;

END IF;

LOOP

FETCH cu_,a(-e...


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DECLARECURSOR e(_cu,o IS

SELECT e(no2 enae FRO# e(;

e(_eco' e(_cu,o1RO3T4PE;BEGIN OPEN e(_cu,o; LOOP FETCH e(_cu,o INTO e(_eco'; ...

DECLARECURSOR e(_cu,o IS

SELECT e(no2 enae FRO# e(;

e(_eco' e(_cu,o1RO3T4PE;BEGIN OPEN e(_cu,o; LOOP FETCH e(_cu,o INTO e(_eco'; ...

Cursors and "ecordsCursors and "ecords

Process the ro's of the acti8e setcon8enient&( )( fetching 8a&ues into a

PL/SQL "EC"#1

E5amp&e


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Cursor ." LoopsCursor ." Loops

FOR record_nameIN cursor_nameLOOP

statement1;

statement2;

. . .

END LOOP;

FOR record_nameIN cursor_nameLOOP

statement1;

statement2;

. . .

END LOOP;

S(nta5

The cursor ." &oop is a shortcut to processcursors1

mp&icit&( opens, fetches, and c&oses cursor1

The record is imp&icit&( dec&ared1


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Cursor ." Loops: %n E5amp&eCursor ." Loops: %n E5amp&e"etrie8e emp&o(ees one )( one unti& no more are"etrie8e emp&o(ees one )( one unti& no more are

&eft1&eft1

E5amp&eE5amp&e

DECLARE CURSOR e(_cu,o IS SELECT enae2 'e(tno FRO# e(;BEGIN

FOR e(_eco' IN e(_cu,o LOOP 55 6(-6c6t o(en an' 6(-6c6t 7etc8 occu IF e(_eco'.'e(tno ! )0 THEN ... END LOOP; 55 6(-6c6t c-o,e occu,END;

DECLARE CURSOR e(_cu,o IS SELECT enae2 'e(tno FRO# e(;BEGIN

FOR e(_eco' IN e(_cu,o LOOP 55 6(-6c6t o(en an' 6(-6c6t 7etc8 occu IF e(_eco'.'e(tno ! )0 THEN ... END LOOP; 55 6(-6c6t c-o,e occu,END;


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Seminar e5ercise The purpose of this e5ercise is to create a procedure 'hich, 'hen

e8o-ed, 'i&& increase the sa&ar( of a grade )( > or ;

depending on the &e8e& of the grade1 ou 'i&& need to popu&ate the

ta)&e first 'ith a minimum of ; entries, the empgrade 8a&ue shou&d

)e )et'een ; and >, and the idea is the higher the grade the higher the

manager1 There is a script for this on the B&ac-Board1

nce (ou ha8e done this (ou shou&d compi&e the code this 'i&& then

indicate if the procedure has compi&ed or not1 f compi&ation is

unsuccessfu& entering the command so/ errors 'i&& &ist an(

pro)&ems 'ith the code1 To run the procedure (ou t(pe execute

0procedure name>at the SQL prompt1

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Procedures and Cursors