CREATE CONVERSION SQL - Language Statements CREATE CONVERSION define a user-defined conversion CREATE [DEFAULT] CONVERSION conversion_name FOR source_encoding TO dest_encoding FROM funcname CREATE CONVERSION defines a new encoding conversion. There are two kinds of conversions. A default conversion is used for an automatic encoding conversion between frontend and backend. There should be only one default conversion for source/destination encodings pair in a schema. None default conversion never be used for the automatic conversion. Instead it can be used for CONVERT() function. To be able to create a conversion, you must have the execute right on the function and the usage right on the schema the function belongs to. DEFAULT The DEFAULT clause indicates that this conversion is the default for this particular source to destination encoding. There should be only one default encoding in a schema for the encoding pair. A default encoding can be used for not only CONVERT() function, but also for the automatic encoding conversion between frontend and backend. For this purpose, two conversions, from encoding A to B AND encoding B to A, must be defined. conversion_name The name of the conversion. The conversion name may be schema-qualified. If it is not, a conversion is defined in the current schema. The conversion name must be unique with in a schema. source_encoding The source encoding name. source_encoding The destination encoding name. funcname The function used to perform the conversion. The function name may be schema-qualified. If it is not, the function will be looked up in the path. The function must have following signature: conv_proc( INTEGER, -- source encoding id INTEGER, -- destination encoding id CSTRING, -- source string (null terminated C string) CSTRING, -- destination string (null terminated C string) INTEGER -- source string length ) returns VOID; Use DROP CONVERSION to remove user-defined conversions. The privileges required to create a conversion may be changed in a future release. To create a conversion from encoding UNICODE to LATIN1 using myfunc: CREATE CONVERSION myconv FOR 'UNICODE' TO 'LATIN1' FROM myfunc; CREATE CONVERSION is a PostgreSQL extension. There is no CREATE CONVERSION statement in SQL99. , , PostgreSQL Programmer's Guide