Invalid expression in WHERE clause of Transact-SQL outer join

Error constant SQLE_INVALID_TSQL_OJ_EXPRESSION
ODBC 2 State 37000
ODBC 3 State 42000
Severity 16
SQLCODE –680
SQLSTATE 52W23
Sybase error code 301
Probable cause

An expression in the WHERE clause of a query that uses Transact-SQL syntax contains a comparison of a column from the NULL-supplying table with a subquery or an expression that references a column from another table.