SQL Tutorial : DRL / DQL - IF THEN ELSE LOGIC ,CASE, DECODE

SQL Tutorial : DRL / DQL - IF THEN ELSE LOGIC

Let's learn about next topic: IF THEN ELSE LOGIC

IF THEN ELSE LOGIC:

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CASE:

- SELECT LAST_NAME,JOB_ID,

CASE JOB_ID WHEN 'SA_REP' THEN 'SALES REPS'

WHEN 'SA_MAN' THEN 'SALES MANAGERS'

ELSE 'SOME OTHER DESIGNATIONS' END

FROM EMPLOYEES

DECODE

- SELECT LAST_NAME,JOB_ID,

DECODE( JOB_ID ,'SA_REP' ,'SALES REPS',

                                               'SA_MAN' ,'SALES MANAGERS',

           'SOME OTHER DESIGNATIONS' ) "EMP DETAILS"

FROM EMPLOYEES

Point to Note:
CASE:
- ANSI SQL
- STATEMENT
- CANNOT USE NULL COMPARISONS

- CAN USE RELATIONAL OPERATORS

- CAN BE USED AS A PART OF PLSQL EXPRESSIONS

DECODE :

- FUNCTION

- CAN USE NULL COMPARISONS

- CANNOT USE RELATIONAL OPERATORS

                +

- CANNOT BE USED AS A PART OF PLSQL EXPRESSIONS

- MULTIPLE I/P THEN MULTIPLE ROW FUNCTIONS OR

AGGREGATE FUNCTIONS