Net.Data Reference Guide

Conditional Variables

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The value of a conditional variable is conditionally set based on the value of another variable or string. This is also called a ternary operation.

test ? trueValue : falseValue

test

A condition to test.

trueValue

The value to use if the test is true.

falseValue

The value to use if the test is false.

Example 1: If varB exists, varA=value_1, otherwise varA=value_2.

varA = varB ? "value_1" : "value_2"

Example 2: In this case, varname is null if value_1 is null, otherwise varname is set to value_1.

varname = ? "$(value_1)"

Example 3: Conditional and LIST variables are most effective when used together. This example shows how to set up a WHERE list in the DEFINE block. The variables cust_inp and prod_inp are HTML input variables passed from CGI, usually from an HTML form. The variable where_list is a LIST variable made of two conditional statements, each statement containing a variable from CGI.

%DEFINE{
%list " AND " where_list
where_list    =  ? "custid = $(cust_inp)"
where_list    =  ? "product_name LIKE '$(prod_inp)%'"
where_clause  =  ? "WHERE $(where_list)"
%}
 
%FUNCTION(DTW_SQL) mySelect() {
   SELECT * FROM prodtable $(where_clause)
%}

If CGI returns values for both variables cust_inp and prod_inp, for example, IBM and 755C, the where_clause is:

WHERE custid = IBM AND product_name LIKE '755C%'

If either variable cust_inp or prod_inp is null or not defined, the WHERE clause changes to omit the null value. For example, if prod_inp is null, the WHERE clause is:

WHERE custid = IBM

If both values are null or undefined, the variable where_clause is null and no WHERE clause appears in SQL queries containing $(where_clause).