# Expression Types

In SQL Query Builder, you can use build expressions of these types when creating SQL statements.

Table 1. Expression types
Type | Description
--- | ---

Function

A function returns a value. Functions types include column functions, scalar functions, row functions, or table functions.

- The argument of a column function is a collection of like values (a column). This function can return a NULL value.
- The argument(s) of a scalar function are individual scalar values, which can be of different types. This function can return a NULL value.
- The argument of a row function is a structured type. The function returns a row of built-in data types and can only be specified as a transform function for a structured type.
- The argument(s) of a table function are individual scalar values, which can be of different types. The function returns a table, and can be specified only within the FROM clause of a SELECT statement.

CASE

CASE expressions allow an expression to be selected based on the evaluation of one or more conditions. A CASE expression contains one or more when clauses of either Search or Simple type.

- A Search CASE expression contains a condition that is evaluated, such as i<8.
- A Simple CASE expression determines if the when clause evaluates to true; otherwise, the else clause determines the value of the case-expression.

CAST | A CAST function converts instances of a datatype to instances of a different datatype.

Constant

A constant specifies a value: a string or a number.

- Numeric constants can be an integer, floating-point, or decimal.
- A string constant can be a character string, hexadecimal, or a host variable name. A colon precedes the host variable name, for example, :var. The host variable becomes a value when the statement is executed.

Subquery | A subquery is a SELECT, WITH, or FULLSELECT statement nested within another SQL statement. The expression value is the result of the subquery.
Build up expressions by operators | You can build an expression by applying operators to columns or expressions such as x+y where x is a column and y is an expression.

Related tasks
Building Expressions