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 = expressionThe 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.