The IF Statement

Relates conditions to actions.

IF condition THEN

    then block

[ELSEIF condition THEN

    elseif block]

[ELSE

else block]

END IF;

Example

DEFINE R1 TYPE(FB) DATA(

A SMALLINT,

B SMALLINT,

C SMALLINT,

D SMALLINT,

E SMALLINT)

DSNAME 'IBMUSER.Files.R1';

 

IF R1.C = R1.A THEN;

R1.B = R1.A;

ELSEIF R1.C = 456 THEN;

R1.E = 1234;

ELSEIF R1.C = 567 THEN;

R1.B = 123;

ELSE;

R1.D = R1.A;

END IF;

 

The keyword THEN is optional.

 

The IF statement is used to relate conditions to actions. Conditions are tested from the top: the first true condition causes the corresponding block to be executed, and following conditions and statements to be ignored. Unconditional execution resumes after END IF.

 

A block can contain zero or any number of statements. For example this is perfectly valid, meaning Do nothing if R1.C = R1.A

IF R1.C = R1.A THEN;

ELSEIF R1.C = 456 THEN;

R1.E = 1234;

END IF;

 

A block can contain further logic-control statements: for example

IF R1.C = R1.A THEN;

IF R1.C = 456 THEN;

R1.E = 1234;

END IF;

ELSEIF R1.C = 456 THEN;

R1.E = 1235;

END IF;

 

By the way, this particular example could be written without a nested IF as: -

IF R1.C = R1.A & R1.C = 456 THEN;

R1.E = 1234;

ELSEIF R1.C = 456 THEN;

R1.E = 1235;

END IF;

 

Any inner logic must be completed with appropriate END IF, END FOR, or END CASE statements before the outer IF statement is resumed.

 

Conditions, which are described here, are essentially the same wherever a condition is written: in IF and ELSEIF statements, in WHERE and UNTIL options of FOR and I/O statements (GET, PROCESS, UPDATE, DELETE).