MDAC 2.5 SDK - ODBC Programmer's Reference
Appendix C: SQL Grammar
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 |