Embedded Sql.rtf

8/14/2019 Embedded Sql.rtf

1/20

ERIS (EMBEDDED SQL)

What SQL provides to AS/400 ?

0* SQL run-time support

1* SQL pre-compilers

2* SQL interactive interface

3* Run SQL Statements CL command

4* DB2/ !! Quer" Mana#er

SQL run-time support

SQL run-time parses SQL statements and runs an" SQL statements$ %S/ !!

supports t&is in a'sence of DB2 Quer" Mana#er SQL Development it$ *t is an

inte#ral part of %S/ !!$

SQL pre-compilers

SQL pre-compilers support pre-compilin# em'edded SQL statements in &ost

lan#ua#es$ +&e SQL &ost lan#ua#e pre-compilers prepare an application

pro#ram containin# SQL statements$ +&e &ost lan#ua#e compilers t&en compile t&e

pre-compiled &ost source pro#rams$


2/20

SQL interactive interface

SQL interactive interface allo,s "ou to create and run SQL statements$

Run SQL statements CL command

R .SQLS+M allo,s "ou to run a series of SQL statements ,&ic& are stored in a

source file$ +&e R .SQLS+M command is part of t&e DB2/ !! Quer" Mana#er and

SQL Development it$

D !/400 Quer" #ana$er

DB2/ !! Quer" Mana#er provides a prompt-driven interactive interface t&at allo,s

"ou to create data add data maintain data and run reports on t&e data'ases$

Quer" Mana#er is part of t&e DB2/ !! Quer" Mana#er and SQL Development it$

Steps in Creatin$ Application pro$ram

5* %ser source code mem&er

0 source code is ,ritten in R1 LE alon# ,it& SQL statements in a source mem'er

usin# SE $

6* 'emporar" Source (ile #em&er

+&is source is pre-compiled usin# CR+SQLR1 * command ,&ic& creates a


3/20

temporar" source file QSQL+EM13 in Q+EM1 ,&ic& is deleted after 4o' completion$+&is mem'er t&en contains 5

Calls to the SQL run-time support, which have replaced embedded SQLstatements

Parsed and syntax checked SQL statements

7* # odule

0 module is created usin# command CR+R1 M%D$

Modules contain information a'out t&e SQL statements6 &o,ever t&e SQLaccess plans are not created until t&e modules are 'ound into eit&er a

pro#ram or service pro#ram$


4/20

8* )ro$ram

0 pro#ram is t&e o'4ect ,&ic& "ou can run t&at is created as a result of t&ecompile process for non-*LE compiles or as a result of t&e 'ind process for

*LE compiles$

0n Access plan is a set of internal structures and information t&at tells SQL&o, to run an em'edded SQL statement most effectivel"$ *t is created onl",&en t&e pro#ram &as 'een created successfull"$

0ccess plans are stored and maintained in t&e pro#ram o'4ect for non-distri'uted SQL pro#rams and in t&e SQL pac7a#e for distri'uted SQLpro#rams$

Cursors

9* 0 cursor provides a ,a" to access a ta'le$

10* *t is used ,it&in an SQL pro#ram to maintain a position in t&e ta'le$

11* SQL uses a cursor to ,or7 ,it& t&e ro,s in t&e ta'le and to ma7e t&emavaila'le to t&e pro#ram$

12*+&e pro#ram can &ave several cursors alt&ou#& eac& must &ave a uni8uename$

'"pes of Cursors

13* Serial Cursor Scrolla'le Cursor

Serial Cursor

14* 0 Serial cursor is one defined ,it&out t&e SCR%LL 7e",ord$

15* 9or a Serial cursor eac& ro, of t&e ta'le can 'e fetc&ed onl" once per %1E.of t&e cursor$


5/20

16* :&en t&e Serial cursor is opened it is positioned 'efore t&e first ro, in t&eta'le$

17* :&en a 9E+C; is issued t&e Serial cursor is moved to t&e ne


6/20

NEXT 1ositions t&e cursor on t&e ne n ?

in relations&ip to t&e cursor@s current position$

%sin$ Cursors

Step 35 Define t&e Cursor

Step 25 %pen t&e Cursor

Step A5 Specif" :&at to Do :&en End-of-Data *s

Reac&ed

Step 5 Retrieve a Ro, sin# a Cursor

Step 5 pdate t&e Current Ro,

Step 5 Delete t&e Current Ro,

Step 5 Close t&e Cursor

Step *+ Define the Cursor

E EC SQL (Serial)

DECL0RE cursor-name C RS%R 9%R

SELEC+ column-3 column-2 $$$

9R%M ta'le-name $$$

9%R 1D0+E %9 column-2 $$$


7/20

E.D-E EC$

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

E EC SQL (Scrollable)

DECL0RE cursor-name DF.0M*C SCR%LL

C RS%R 9%R

SELEC+ column-3 column-2 $$$

9R%M ta'le-name $$$

:;ERE column-3 G e


8/20

Step 4+ Retrieve a ro2 usin$ Cursor

E EC SQL (Serial)

9E+C; cursor-name

*.+% 5&ost varia'le-3H 5&ost varia'le-2I $$$

E.D-E EC$

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

E EC SQL (Scrollable)

9E+C; REL0+*=E inte#er

9R%M cursor-name

*.+% 5&ost varia'le-3H 5&ost varia'le-2I $$$

E.D-E EC$

Step 3+ %pdate the Current Ro2

E EC SQL (Serial/Scrollable)

1D0+E ta'le-name

SE+ column-3 G value H column-2 G valueI $$$

:;ERE C RRE.+ %9 cursor-name

E.D-E EC$

Step + Delete the Current Ro2


DELE+E 9R%M ta'le-name

:;ERE C RRE.+ %9 cursor-name

E.D-E EC$


9/20

Step 5+ Close the Cursor


CL%SE cursor-name

E.D-E EC$

+&e cursor is closed '" t&e s"stem automaticall" ,&en

23* 0 C%MM*+ ,it&out ;%LD statement is issued and t&e cursor is not declaredusin# t&e :*+; ;%LD clause

24* A R,LL AC6 2ithout 7,LD statement is issued

25* +&e 4o' ends

26* +&e activation #roup ends CL%SQLCSR(JE.D0C+ R1) ,as specified on t&epre-compile

27* +&e first SQL pro#ram in t&e call stac7 ends and neit&erCL%SQLCSR(JE.DK%B) or CL%SQLCSR(JE.D0C+ R1) ,as specified ,&en t&epro#ram ,as pre-compiled$

28* 0n JR : C%..EC+ occurred$

Because an open cursor still &olds loc7s on referred-to-ta'les or vie,s "ou s&ould

e


10/20

#ultiple-Ro2 (.'C7

29* Sin#le 9E+C; statement to retrieve multiple ro,s (Ma


11/20

#ultiple-Ro2 (.'C7

%sin$ a 7ost Structure Arra"

33* 1ro#ram &as a ;ost Structure 0rra" and an associated *ndicator 0rra"

34* +&e ;ost Structure 0rra" consists of an arra" of structures eac& structurecorresponds to one ro, of t&e ta'le

35* Bot& t&e arra"s &ave same dimension

%sin$ a Ro2 Stora$e Area

36* 1ro#ram &as a Ro, Stora#e 0rea and an associated D escriptor Area(SQLDA)

37* Ro, Stora#e 0rea is a &ost varia'le can 'e JC;0R t"pe enou#& to &old allt&e ro,s fetc&ed

38* SQLD0 contains SQL+F1E SQLLE.

)ro$rammin$ considerations

39* eneral uidelines

40* *nde< Considerations

41* Codin# 0lternatives

42* Loc7in# 0nd Concurrenc"

8eneral 8uidelines

43* 0void .umeric Conversions

SELEC+ 0 *.+% 5B


12/20

:;ERE 0 G 5B

44* Select %nl" t&e columns .eeded

0void SELEC+ J

se 9%R 1D0+E %9 $$$

45* Se8uence %nl" :&en .ecessar"

0void %RDER BF$$

Consider an *.DE

nde9 Considerations

46* SQL maintains t&e *.DE

47* SQL decides ,&et&er to use t&e *.DE

48* *.DE 'ased retrieval is usuall" more efficient t&an +0BLE SC0.

49* *nde


13/20

Codin$ Alternatives

58* R%: SELEC+*%. is faster t&an pro#rammin#

59* C% .+ M0 M*. 0= S M and R% 1 BF are more efficient t&anpro#rammin#

60* SQL ,ill not use an inde< for +:% 1RED*C0+ES ,&ic& use an %R

0 G %R BG (no inde< used)

(0G or 0GA) and BN (inde0BCP? (inde< :*LL 'e used)

L* E >P0BC? (inde< :*LL .%+ 'e used)

62* SELEC+ :;ERE C3G 5;= 3!!

CANN ! use index, but ;= G ;= 3!!

SELEC+ :;ERE C3 G 5;=

CAN use "N#$%

63* SELEC+ 9R%M +EM1L :;ERE DE1+ G >032?

%R DE1+ N >B32?

CANN ! use "N#$% , &'!

SELEC+ 9R%M +EM1L :;ERE DE1+ G >032?

.*%. 0LL

SELEC+ 9R%M +EM1L :;ERE DE1+ G >B32?

CAN use "N#$%

Loc:in$ ; Concurrenc"


14/20

64* 0 mec&anism to ensure data inte#rit"

65* 1revents access to inconsistent data

66* 0n" data 'ein# c&an#ed '" "our pro#ram is not availa'le to ot&ers until "ourelease it

+&ree levels of loc7in# in SQL/ !!

REC%RD - C%MM*+(J.%.E)

+R0.S0C+*%. - C%MM*+(J0LL)

9*LE - L%C +0BLE E CL S*=E

LOCK TABLE

>>-------- LOCK TABLE ---table_name --IN-----SHARE------MODE----->< [EXCLUSIVE

Codin$ SQL statements in L. R)8


15/20

67* SQLCA SQL Communication Area1

68* +&e SQL pre-compiler automaticall" places t&e SQLC0 in t&e definitionspecifications of t&e *LE R1 / !! pro#ram prior to t&e first calculationspecification

69* %nl" 3 SQLC0 per pro#ram (3A len#t&)

70* SQLC0 #ives SQLC%DE of last statement retrieved

71* SQLC%DE G ! successful operation

72* SQLC%DE ! error

73* SQLC%DE N ! ,arnin#

74* SQLC%DE G 3!! end of data

75* SQLDA SQL Descriptor Area1

76* Multiple SQLD0s per pro#ram ( ! len#t&)

77* SQL 'uilds SQLD0 at runtime

78* SQL pre-compiler allocates static stora#e to SQLD0

79* *f t&e called pro#ram also contains SQL statements it s&ould 'e ended ,it&SE+%. R+ and not SE+%. LR as t&e later initialiTes t&e static stora#e and SQLD0

9ollo,in# statements re8uire SQLD0

E EC +E$$$ S*. DESCR*1+%R descriptor-name

9E+C;$$$ S*. DESCR*1+%R descriptor-name

%1E.$$$ S*. DESCR*1+%R descriptor-name

DESCR*BE statement-name *.+% descriptor-name

DESCR*BE +0BLE &ost-varia'le *.+% descriptor-name

1RE10RE statement-name *.+% descriptor-name


16/20

7ost varia&les

80* 0ll &ost varia'les must 'e preceded '" a colon (5)

81* Date and +ime &ost varia'les are assi#ned to correspondin# Date and +imesu'-fields in su'structures #enerated '" SQL pre-compiler$ enerated su'-fieldsare declared usin# some date format$ *f D0+9M+ is in s"stem format(JMDF JFMD JDMF JK L) valid values for &ost varia'les are 'et,een 3U ! and2!AU$ 9or an" value outside t&is limit use *BM SQL format (J*S% J S0 JE RJK*S)$

82* 9ollo,in# t"pe of varia'les are not allo,ed as ;ost varia'les$

Pointer, !ables, '#A!$, '#A(, ') N!*, '($A+, Named constants, )ulti-dimension arrays


17/20

Data structure as 7ost varia&le

!"""#""""$""""%""""$""""&""""$""""'""""$

D EM(LO)EE DS

D EM(NO *# *+A

D ,NAME * #.A

D MIDINT #/ #/A

D LNAME %* &'A

D DE(TNO &0 & A

C MOVE 1***%%*1 EM(NO

C2EXEC S3L

C$ SELECT ! INTO 4 EM(LO)EE

C$ ,ROM COR(DATA"EM(DATA

C$ 5HERE EM(NO 6 4EM(NO

C2END-EXEC

Data structure Arra" as 7ost varia&le

!"""#""""$""""%""""$""""&""""$""""'""""$

DDE(ARTMENT DS OCCURS7#*8

D DE(TNO *# *&A

D DE(TNM *' &%A

D M9RNO && &.A

DIND_ARRA) DS OCCURS7#*8

D INDS &B * DIM7&8

"""

C2EXEC S3L

C$ DECLARE C# ,OR


18/20

C$ SELECT ! ,ROM COR(DATA"DE(ARTMENT

C2END-EXEC

"""

C2EXEC S3L C$ ,ETCH C# ,OR #* RO5S

C$ INTO 4DE(ARTMENT4IND_ARRA)

C2END-EXEC


19/20

%sin$ .9ternal (ile Descriptions

!"""#""""$""""%""""$""""&""""$""""'""""$""""0""""$""""+""""$"""" """

,DE(ARTMENTI( E DISK RENAME7ORI9REC4DE(TREC8

Code t&e file on 9-Specs onl" if it is to 'e used '" R1 LE

statements else define file(ta'le) as e


20/20

SQLC%DE #ives t&e status of last operation$

/E EC SQL

:;E.E=ER condition action

/E.D-E EC

Conditions 5SQLERR%R

SQL:0R.*.

.%+ 9% .D

0ctions 5 %+% 5ERR

C%.+*. E

*n case ,e use %+% +0 statement can precede an SQL statement$

Documents

Embedded Sql.rtf