Parameter Data Types

Even though each parameter specified with SQLBindParameter is defined using an SQL data type, the parameters in an SQL statement have no intrinsic data type. Therefore, parameter markers can be included in an SQL statement only if their data types can be inferred from another operand in the statement. For example, in an arithmetic expression such as ? + COLUMN1, the data type of the parameter can be inferred from the data type of the named column represented by COLUMN1. An application cannot use a parameter marker if the data type cannot be determined.

The following table describes how a data type is determined for several types of parameters, in accordance with SQL-92. For a more comprehensive specification on inferring the parameter type when other SQL clauses are used, see the SQL-92 specification.

Location of parameter

Assumed data type

One operand of a binary arithmetic or comparison operator

Same as the other operand

The first operand in a BETWEEN clause

Same as the second operand

The second or third operand in a BETWEEN clause

Same as the first operand

An expression used with IN

Same as the first value or the result column of the subquery

A value used with IN

Same as the expression or the first value if there is a parameter marker in the expression.

A pattern value used with LIKE

VARCHAR

An update value used with UPDATE

Same as the update column