6.2.1 C API Prepared Statement Type Codes (original) (raw)

6.2.1 C API Prepared Statement Type Codes

The buffer_type member ofMYSQL_BIND structures indicates the data type of the C language variable bound to a statement parameter or result set column. For input, buffer_type indicates the type of the variable containing the value to be sent to the server. For output, it indicates the type of the variable into which a value received from the server should be stored.

The following table shows the permissible values for thebuffer_type member ofMYSQL_BIND structures for input values sent to the server. The table shows the C variable types that you can use, the corresponding type codes, and the SQL data types for which the supplied value can be used without conversion. Choose the buffer_type value according to the data type of the C language variable that you are binding. For the integer types, you should also set theis_unsigned member to indicate whether the variable is signed or unsigned.

Table 6.1 Permissible Input Data Types for MYSQL_BIND Structures

Use MYSQL_TYPE_NULL as indicated in the description for the is_null member inSection 6.2, “C API Prepared Statement Data Structures”.

For input string data, use MYSQL_TYPE_STRING or MYSQL_TYPE_BLOB depending on whether the value is a character (nonbinary) or binary string:

• MYSQL_TYPE_STRING indicates character input string data. The value is assumed to be in the character set indicated by thecharacter_set_client system variable. If the server stores the value into a column with a different character set, it converts the value to that character set.
• MYSQL_TYPE_BLOB indicates binary input string data. The value is treated as having thebinary character set. That is, it is treated as a byte string and no conversion occurs.

The following table shows the permissible values for thebuffer_type member ofMYSQL_BIND structures for output values received from the server. The table shows the SQL types of received values, the corresponding type codes that such values have in result set metadata, and the recommended C language data types to bind to the MYSQL_BIND structure to receive the SQL values without conversion. Choose thebuffer_type value according to the data type of the C language variable that you are binding. For the integer types, you should also set the is_unsigned member to indicate whether the variable is signed or unsigned.

Table 6.2 Permissible Output Data Types for MYSQL_BIND Structures