`<let>`

<let> is used within a <block>, or independently in place of a <block>, and can be used to assign new values to variables defined within the block or to define new variables.

Description

The form <let [VAR_1]="A" [VAR_2]="B"> [CONTENTS] </let> expands [CONTENTS] with [VAR_1] and [VAR_2] defined. The values of these variables may be referenced (along with other block variables) with the {@[VAR]} syntax within expressions in [CONTENTS].

Variables defined within a <let> only have scope within the <let></let> element itself.

Note: In many cases, the <let> element can be used in the same way a <block> is used, only without the name="[BLOCK_NAME]" portion of the opening tag.

Syntax

<let [USER_DEFINED_VAR_1]="[VALUE_1]" ...
          [USER_DEFINED_VAR_N]="[VALUE_N]">
     [CONTENTS]
</let>

Attributes

[USER_DEFINED_VAR_x]: Accepts a string that will act as a user-defined variable. The variable name must begin with a lowercase alphabetic character and consist only of lowercase alphanumeric characters, digits, and/or underscores.
The block element may include any number of additional attributes, which may be used as parameters in the Macro Language code contained within the element. The value of a user-defined variable (e.g., my_var) is substituted wherever a scalar expression containing a reference to it (e.g., {@my_var}) appears within the block element.

Example

In this example, the base table is pub.demo.retail.item. The goal is to parameterize a selection statement so that both the column and the comparison value can be provided independently of the selection statement itself.

<base table="pub.demo.retail.item"/>
<let column="sales" val="1.25">
    <sel value="{@column}>{@val}"/>
</let>

This query expands to:

<sel value="sales>1.25"/>