20.1.2.1 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.

Figure 20-5 Error Message Displays When Expression Evaluates to False

Description of "Figure 20-5 Error Message Displays When Expression Evaluates to False"