IF … THEN … ELSE

Data Manipulation (DML) StatementsBuilt-in Scalar Functions

`IF … THEN … ELSE`

Conditional branching

Syntax

IF (<condition>)
  THEN <compound_statement>
  [ELSE <compound_statement>]

Table 1. `IF … THEN … ELSE` Parameters
Argument	Description
condition	A logical condition returning `TRUE`, `FALSE` or `UNKNOWN`
compound_statement	A single statement, or statements wrapped in `BEGIN … END`

The conditional branch statement IF … THEN is used to branch the execution process in a PSQL module.The condition is always enclosed in parentheses.If the condition returns the value TRUE, execution branches to the statement or the block of statements after the keyword THEN.If an ELSE is present, and the condition returns FALSE or UNKNOWN, execution branches to the statement or the block of statements after it.

Multi-Branch Decisions

PSQL does not provide more advanced multi-branch jumps, such as CASE or SWITCH.However, it is possible to chain IF … THEN … ELSE statements, see the example section below.Alternatively, the CASE statement from DSQL is available in PSQL and is able to satisfy at least some use cases in the manner of a switch:

CASE <test_expr>
  WHEN <expr> THEN <result>
  [WHEN <expr> THEN <result> ...]
  [ELSE <defaultresult>]
END

CASE
  WHEN <bool_expr> THEN <result>
  [WHEN <bool_expr> THEN <result> ...]
  [ELSE <defaultresult>]
END

Example in PSQL

...
C = CASE
      WHEN A=2 THEN 1
      WHEN A=1 THEN 3
      ELSE 0
    END;
...

`IF` Examples

An example using the IF statement.Assume that the variables FIRST, LINE2 and LAST were declared earlier.
```
...
IF (FIRST IS NOT NULL) THEN
  LINE2 = FIRST || ' ' || LAST;
ELSE
  LINE2 = LAST;
...
```
Given IF … THEN … ELSE is a statement, it is possible to chain them together.Assume that the INT_VALUE and STRING_VALUE variables were declared earlier.
```
IF (INT_VALUE = 1) THEN
  STRING_VALUE = 'one';
ELSE IF (INT_VALUE = 2) THEN
  STRING_VALUE = 'two';
ELSE IF (INT_VALUE = 3) THEN
  STRING_VALUE = 'three';
ELSE
  STRING_VALUE = 'too much';
```
This specific example can be replaced with a simple CASE or the DECODE function.

IF …​ THEN …​ ELSE

IF …​ THEN …​ ELSE

IF Examples

IF … THEN … ELSE

`IF … THEN … ELSE`

`IF` Examples