The LENGTH() function in SQL

The semantics of the LENGTH() SQL function differs according to the database engine.

The SQL LENGTH() function must be used with care: Each database server has different semantics for this function, regarding length and trailing blanks handling.

Note: The language provides a LENGTH built-in function which is part of the runtime system. Do not confuse this with the SQL LENGTH() function, used in SQL statements. The LENGTH() function of the language returns zero when the string expression is NULL.

Table 1. Database server support of LENGTH()
Database Server Type	Function name	Counting unit	Significant trailing blanks for CHAR() columns	Return value when NULL
Genero db	LENGTH(expr)	Octets	No	NULL
IBM^® DB2^® UDB	LENGTH(expr)	Octets	Yes	NULL
IBM Informix^® (1)	LENGTH(expr)	Octets	No	NULL
Microsoft™ SQL Server (2)	LEN(expr)	Characters	No	NULL
MySQL	LENGTH(expr)	Characters	No	NULL
Oracle Database Server	LENGTH(expr)	Characters	Yes	NULL
PostgreSQL	LENGTH(expr)	Characters	Yes	NULL
Sybase ASE (2)	LEN(expr)	Characters	No	NULL
SQLite	LENGTH(expr)	Characters	Yes	NULL

Search for LENGTH() usage in your SQL statements and review the code of the database-specific function.