DB2 Basics - Quick Refernce

8/8/2019 DB2 Basics - Quick Refernce

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Mainframe For Dummies

DB2 Basics - Quick Refernce

Relational Database Management System(RDBMS) Universal Database(UDB)

This is one of the sub systems in Mainframes.

Any number of Sub Systems can be created in Mainframesas per the requirements.

Hierarchy of DB2 Sub system:
http://mainframe-faqs.blogspot.com/http://mainframe-faqs.blogspot.com/2008/02/db2-basics-quick-refernce-relational.htmlhttp://mainframe-faqs.blogspot.com/http://mainframe-faqs.blogspot.com/2008/02/db2-basics-quick-refernce-relational.html


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TS Table Space INS Index Space

T Table IND Index

V view

Maximum storage space for a Table Space is 64 millionbytes.

SQL can be used to Create, Delete, and Update and Querythe Objects

SQL queries can be executed by the following techniques


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1. Application programming2. Tools like QMF (Query Management Facility)

SPUFI (SQL Processor User File Input)

DATA TYPES :

Integer -- 4 bytes

Small int -- 2 bytes

Char(n) N bytes

Varchar(n) N+2 bytes

Graph(n) 2n bytes

Vargraph(n) 2N+2 bytes

Date 10 bytes

Time 8 bytes

Timestamp 26 bytes

NORMALIZATION :

Arranging the data in the Database in organized manner.

1NF: Avoiding multiple values or set of values in one column.

2NF: Avoiding repeated rows by defining primary key.

3NF: Separating functionally dependent and non-functionallydependent columns


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Primary key :-

Uniquely identified row Which can be formed with single or multiple columns Does not allow duplicate records Cannot contain Null

Foreign key : -

Another identifier which can be used to buildrelationship between the tables

Must be the primary key of parent table with same datatype & length

Can consists of single or multiple columns Can contain Null or duplicate rows Multiple foreign keys can be defined in one table Foreign key should be defined at the time of defining

child table in the create command by WITH

REFERENCES option.

CREATE TABLE ITEM(

INO INTEGER,

INAME CHAR(15),

CNO INTEGER,

PRIMARY KEY IS INO,

FOREIGN KEY IS CNO

WITH REFERENCES CUST)


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REFERENCE INTEGRITY:

The relationship between two tables which can beachieved by defining foreign key.

PRIMARY KEY FOREIGN KEY

Cannot contain Null values orduplicate rows

Can contain Null values orduplicate rows

Cannot be updated Can be updated

Can be defined as a foreignkey in other table

which must be primary key ofanother table

only one primary key can bedefined for one table

multiple foreign keys can bedefined for one table

SQL(Structured Query Language)

DDL (Data Definition Language)

Create, alter, drop


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DML (Data Manipulation Language)

Insert, update, select & delete

DCL (Data Control Language)

Grant, Revoke

TCL (Transaction Control Language)

Commit, Rollback

Some SQL Quries

Static SQL for Insert: Insert into cust(cno, cname, cloc)

values (10, xyz, hyd)

Dynamic SQL for Insert: Insert into cust(cno, cname, cloc)values (v1, v2, v3)

v1,v2, v3 are host variables to be defined in working storagesection.

Delete from cust

Delete from cust where cno = 20


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Update cust set cname = xyz where cno = 20

Select cno,cname from cust

Select * from cust

Select * from, cust where cno = v1

Select * from cust wehre cno=v1 and cname =v2

Select * from cust where cno between 20 and 60

Select * from cust where cname like %y%

Column functions:

Select max(sal) from emp

Select min(sal) from emp

Select avg(sal) from emp

Select sum(sal) from emp

Above statement returns Null values if no row exits for

specified condition

To avoid duplicate rows : select distinct cno,cname from cust

To get total no. of rows : select count(*) from cust


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Above statement returns Zeros if no row exits for specifiedcondition

SUBQUERY:

Query within Query First inner query executes & out query executes based

on the result of inner query Max of 15 sub queries can be coded To simplify sub queries, logic can be built with

combination of COBOL + SQL statements

To retrieve second maximum salary from emp table:

Select max(sal) from emp where sal


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Host variables:

Can be used to pass the data from cobol program toDB2 table or DB2 table to COBOL program.

When host variables are coded with sql statements itmust be prefixed with : like :hv-cname.

Table name must be supplied as input to DCLGEN &partition dataset should be as output.

After creating DCLGEN variables which must be copiedto application program in WORKING-STORAGE SECTIONby using include command i.e.

Exec sql

Inlcude custDCL

End-exec.

Include & copy have the same functionality

SQLCODE :

Predefined numeric number which can be used to checkSQL statements for successful , unsuccessful execution.

SQLCODE can be stored in SQLCA(SQL CommunicationArea) Copy SQLCA in WORKING-STORAGE SECTION System defined variable Evaluate or if statement must be coded to check the

SQLCODE immediately after SQL statement. SQLCODE =00 ---- successful


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= +100 --- end of table or record not found.

Sample program:

WORKING-STORAGE SECTION.

EXEC SQL

INCLUDE SQLCA

END-EXEC

EXEC SQL

INCLUDE CUSTDCL

END-EXEC.

01 WS-SQL-CODE PIC S9(4)

88 88-SUCCESS VALUE 00

88 88-NOTFOUND VALUE 100

88 88-FORIENG KEY VOILATION VALUE 532

88 88- MULITPLE ROW VALUE 811


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PROCEDURE DIVISION.

UPDATE CUST

SET CNAME = :HV-CNAME

WHERE CNO=:HV-CNO

MOVE SQLCODE TO WS-SQLCODE.

EVALUE WS-SQL-CODE

WHEN 88-SUCCESS

DISPLAY SUCCESSFULLY UPDATED

WHEN 88-NOTFOUND

DISPLAY RECORD NOT FOUND

WHEN 88-FOREIGNKEYVOILATION

DISPLAY FOREIGN KEY VOILATION

WHEN OTHER

DISPLAY ERROR OCCURRED IN UPDATE

STOP RUN

END-EVALUATE.

STOP RUN.

CURSOR:


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To retrieve multiple rows for a given condition.

Let us take the following example:

Exec sql

Select cno,cname,cloc

into :hv-cno,:hv-cname,:hv-cloc

from cust where cloc =:hv-cloc

end-exec.

If the condition satisfy for one row it executes successfully. Ifthe condition satisfy for multiple rows it wont work. It returns811 as SALCODE. For this we use cursors.

Cursors can be used to retrieve multiple rows for agiven condition

Cursor cycle is Declare ---> Open ----> Fetch ----->Close

Declare: declares or define name for cursor against atable

Can be coded in working-storage section or procedure

division

For better readability code in working-storage section.

Open:can be used to open a cursor with rows for agiven conditions inbuffer.

Retireves data in to buffer


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Must be coded in the procedure division only

Where condition value must be supplied beforeopening a cursor.

Fetch:can be used to retrieve rows one by one frombuffer into application prog.

Which must be coded in procedure divison afteropen.

Must be coded with hostvariables

No of host variables in fetch & no of columns inthe declare must be same

Canbe executed multiple times using perform. i.e.till EOT or record not found which can be identifiedby SQLCODE = 100

Close :used to close the cursor

Must be coded in procedure division only

Must be executed after open statement.

Practical examples : Can be used to retrieve the databased on loc, date, products.

EXEC SQL

DECLARE C1 CURSOR FOR

SELECT CNO,CNAME FROM CUST

WHERE CNAME=:HV-CNAME


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END-EXEC.

EXEC SQL

OPEN C1.

END-EXEC.

PERFORM UNTIL SQLCODE= 100

EXEC SQL

FETCH C1 INTO :HV-CNO,:HV-CNAME

END-EXEC

END-PERFORM.

EXEC SQL

CLOSE C1

END-EXEC

For Update of where current of:

Which can be used to update row by row when multiplerows are satisfied.

Before update cursor has to be declared with for updateof column option.

Where current of cursor name option must be used with

update command Withhold: this option can be used to remain cursors

open even after commit statement. Must be coded with cursor statement


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EXEC SQL

DECLARE C2 CURSOR WITH HOLD FOR

SELECT CNO,CNAME FROM CUST

WHERE CNAME=:HV-CNAME

FOR UPDATE OF CNAME

END-EXEC.

EXEC SQL

OPEN C1.

END-EXEC.

EXEC SQL

FETCH C2 INTO :HV-CNO,:HV-CNAME

END-EXEC

EXEC SQL

UPDATE CUST SET CNAME=ABC WHERE CURRENT OFC2.

EMD=EXEC.

EXEC SQL

CLOSE C1

END-EXEC

INDEX:


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Index allows duplicate values unique index doesnt allow duplicate rows cross reference between index table & table is called

clustered index. Create index in1 on cust(cno)

PRIMARY KEY INDEX UNIQUE INDEX

Uniquelyidentified row

Record identifiedbased on the index

Recordsidentified basedon the index

No duplicatedrows, no nullvalues

Duplicate rows, nullvalues are allowed

No duplicaterows

Can consist ofsingle or multiplecolumns

Dan consist ofsingle or multiplecolumns

Can consist ofsingle orcolumns

This will bestored inSYSKEYS.

This is stored inSYSINDEX

This is stored inSYSINDEX

VIEWS:


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CREATE VIEW CVIEW(VCNO,VCNAME,VCLOC) AS

(SELECT CNO,CNAME,CLOC FROM CUST WHERE

CNAME LIKE %X%)

Logical representation of the table Stored in virtual memory Can be derived from single table or multiple tables Views are updateable if they are derived from single

table without any column functions , group by Multiple views can be generated from single table.

Views are stored in sysviews

Advantages of Views:

Data security Data correctness

Logical data independence Part of the information can be visible to the sers Accessing can be faster.

DELETE RULES:

Delete rules can be applied for delete command againstDatabase.

Delete rules are 3 types


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1. on delete cascade all matching child rowswill be deleted automatically when we deleteparent row.

2. on delete restrict all matching rows will be

restricted when we delete parent row whichis default.3. on delete set null all matching child row will

be set to null when we delete parent row.

UNION:

UNION is used to concatenate rows into one table fromsingle or multiple tables.

Rules : no. of columns & data type of both the queriesmust be same. column may be different

UNION can be used to eliminate duplicate rows UNION ALL retrieved duplicate rows also.

SELECT CNO,CNAME FROM CUST WHERE CNO=10

UNION/UNIONALL

SELECT CNO,CNAME FROM ITEM WHERE INO=20

JOINS:

JOINS can be used to concatenate columns from onetable or multiple tables.

JOIN types are :


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1. left outer join : which can be used to retrievematching, non matching rows from leftsidetable

2. right outer join: which can be used to retrieve

matching, non matching rows from right sidetable.3. full outer join: which can be used to retrieve

matching, non matching rows from both thetables.

4. self join or inner join : can be achieved bydefining alias for the table.

EXPLAIN :

It can be used to evaluate the performance of SQL queries.

It can be used to tune SQL queries.

Input is SQL queries and output is plan-table.

For every SQL query one plan-table will generate.

All plan-tables are stored in physical seq file.

Plan table

Query

blockno

Table

Name

No.of

Cols

index

no.of

indexs

owner

jointype

groupby

Cpu

time


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1 Cust 10 In1 1 Custc Self Y 10min

DB2 CATALOG:

Consists of Table pace, Index space, Index, uniqueindex, Views, Alias, synonyms, keys.

When we create table, the details of table are enteredin Systable automatically.

SysIBM.SYSTABLE

TableName

No.ofcols

Ownername

Createdby

Createddate

Createdtime

Cust 10 Abc Xyz 02-apr-2004

0850

Item 15 Mno Rst 06-apr-2004

1020

SysIBM.SYSINDEX


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Indexname

TableName

No.ofcols

Ownername

Createdby

Createddate

Createdtime

In1 Cust 10 Abc Xyz 02-apr-

2004

0850

In2 Item 15 Mno Rst 06-apr-2004

1020

SysIBM.SYSCOLS

Col name Tablename

Indexname

Primarykey

Foreign key

Cno Cust In1 Cno -----

Cname Cust In1 Cno

Cloc Cust In2 cno

Ino Item Ino Cno

Iname Item Ino Cno

Ides Item Ino cno

SysIBM.SYSKEYS: All primary & foreign keys.

Grant table syscols to all

Grant table syscols(select/delete/update) to user1,user2

Revoke table syscols from all.


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CATALOG:

SYSTABLE, SYSCOL, SYSKEYS, SYSINDEX, SYSPKS, SYSFKS,SYSALIAS, SYSSYNONYMS, SYSINDEX,SYSVIEWS,SYSTABLESPACE, SYSINDEXSPACE.

PRECOMPILATION PROCESS:

Pre compiler takes COBOL+DB2 program as input &generates DBRM which will be stored in userdefined PDS asseparate member of Recln=80

DSNHPC --- IBM supplied utility used forprecompilation.

Precompiler functions:

Separates SQL & COBOL statements Check SQL syntaxs Replace all SQL statements with host language call

statements in the compiled program. Which generates timestamp tokens

BIND:


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BIND takes DBRM as input & generate package & applicationplan. The package will be loaded to the directory. Plan will beloaded to sysplans.

Bind functions:

Checks authorization for SQL statement Checks the syntax errors of SQL statements like

1. Missing co name in the select list & used in order by &group by

2. Mismatch columns host variables3. Data type mismatch of columns & host variables4. Indicator variables not declared5. Data truncation.

BIND SUBCOMPONANTS/PARAMETERS:

1. OPTIMIZER:o It generates optimized access path by analyzing

the statistics of SQL statements which will bestored.

o RUNSTATS utility is one of the ISPF panel optionwhich is stored in DB2 defaults option.

o Optimized path is stored in package which is notexecutable module.

2. ISOLATION LEVEL:

Which can be used to lock the database at the time ofexecuting SQL statements.


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Cusrsor stability(CS): It acquires the address of a row.Sets the pointer to a specified row based on SQL query& acquires the lock against that row. Then releases theklock after the transaction before commit.

Repeatable Read(RR): which acquires the address of arow & acquire lock against the page(1 page -4024bytes) & then released the lock after the commitstatements.

Default is RR.

3. RUNTIME SUPERVISOR:

Which is to oversee execution of SQL statements.

Statistics like no of tables, columns, indexes, keys

4. PLAN/APPLICATION PLAN:

It consists of executable module which is actual outputof SQL statements which must be specified in theRUNJCL to execute SQL queries if the program is batchprogram. If the program is online which must be

specified in RCT. Application plan will be loaded to loadmodule with time stamp tokens.

COBOL COMPILATION:


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The compiler takes COBOL statement as input to generateobject program, & loaded to the load module by line/editwith time stamp tokens.

UTILITIES USED:

DSNHPC : system utility pre compiler.

IKJEFT01 or IKJEFT01B --- BIND /Run Cob-DB2 Program

IGYCRCTL or IKFCBLOO --- COBOL compilation


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IEWL or HEWL --- link/edit

INTERVIEW QUESTIONS:(watch this space for moreinfo on below Qns)

1. What is RI ? where did u use RI in your project? Explainwith example?

2. What is the difference between primary key, foreignkey, index & unique index?

3. Can we create index when table has duplicate rows?4. Can we create unique index when table has duplicate

rows?5. Can we create index or unique index on empty table?6. What happens to the package when index is dropped?

Whats the process or steps to be taken?7. How to delete package?8. Where package is stored? How to retrieve package?9. Difference between plan & package?

10. What are the steps to be taken when SQLstatements are changed without changing any COBOLstatements?

11. Do we need to pre compile when index isdropped?

12. Can we bind when table is dropped?13. Can optimized access path consist of multiple

DBRMS.14. What is the significance of timestamp tokens?

15. What is the significance of normalization?16. Where do we specify run program, plan name,library & DB2 subsystem

17. IBM supplied utility to run COBOL + DB218. What is difference between DB2 & COBOL files &

give some example for COBOL files & DB2 tablesrelated to your project?


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19. Can we load data from sequential file to table ortable to sequential file?

20. What are the steps to be followed to developDB2+ COBOL program?

21. Can we prepare a program/compile when DB2system is down?22. How to identify DB2 test or production system by

seeing run JCL?23. What is the output of explain?24. What is the difference between correlated sub

query & sub query?25. How to find 4th max sal?26. How to find nth max sal?27. How to evaluate SQLcodes & where it is stored?

28. How to count total no of unique rows from thetable?

29. How to sum repeated rows?30. How to write a cobol program for above query?

Retrieve row by row & use cobol logic to sum repeatedrows?

31. What is the significance of DCLGEN?32. Where DCLGEN is stored?33. Difference between join & union?

34. difference between UNION & UNIONALL?35. Can be have different col names in union?36. How do u evaluate/tune/analyze SQL queries?37. What are the JCL utilities for compile, pre compile,

bind & link edit?38. Wha5t is the significance of isolated levels?39. Can we alter foreign key?40. Can we alter primary key?41. Can we alter data type & length?42. What are the equivalent cobol variables for

varchar?43. What is the time stamp & its format?


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DB2 Basics - Quick Refernce