Using the LET clause - Cloud

Talend Data Shaping Language Reference Guide

Version
Cloud
Language
English (United States)
Product
Talend Cloud
Module
Data Shaping Language
Content
Design and Development
The LET clause is used to define a variable that can be reused later in the query.
The LET clause should be structured as follows:
LET $variable_name = expression

The variable must start with the $ character and cannot be a hierarchical identifier, for example, $item.index is not a valid variable. The variable must be unique throughout the query. The expression used to specify the value of the variable can be a simple expression or a conditional expression.

The LET clause must be used after a FROM, UNNEST or JOIN clause. If the query block contains a WHERE clause, the LET should be placed before it. For example:
FROM customer
LET $address = concatWith(" ", address.street, address.city)
WHERE hasValue(rating) && rating > 650
SELECT { name, rating, address = $address }

The LET clause is evaluated for each iteration in the query, unlike the WITH clause.