Validating By Returning True/False Result

Validate input with a PL/SQL expression that returns true for valid data and false for invalid data.

The Error Message you configure on a PL/SQL Expression-type validation shows if the expression evaluates to false. A validation named Can’t both start with a 4 uses the expression below. You can read it:

• the data is valid if it’s “not the case that both page items’ first character is a 4”

**not**(    substr(:P3_MULTIPLE_OF_TEN,1,1)      = '4'
    **and** substr(:P3_ODD_MULTIPLE_OF_FIVE,1,1) = '4')

Tip:

Logically, this is identical to the alternative expression below that you can read:

• the data is valid “if either one has a first character that’s not equal to 4”:

   substr(:P3_MULTIPLE_OF_TEN,1,1)      **!=** '4'
**or** substr(:P3_ODD_MULTIPLE_OF_FIVE,1,1) **!=** '4'

The translatable Text Message named CANNOT_BOTH_START has a single placeholder named first_digit:

Cannot both start with a **%first_digit**

The validation Error Message references it by name, and provides the value 4 for the named placeholder:

&{**CANNOT_BOTH_START** **first_digit**="4"}.

The figure shows the Can’t both start with a 4 validation selected in the processing tree and highlights the PL/SQL Expression it uses to test validity as well as the Error Message configured to display when the validation fails by evaluating to false.

Description of the illustration boolean-validation-err-msg.png