| 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.
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| 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.
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| CAST |
A CAST function converts instances of a datatype to
instances of a different datatype.
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| 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.
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| Subquery |
A subquery is a SELECT, WITH, or FULLSELECT statement nested within
another SQL statement. The expression value is the result of the
subquery.
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| 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. |