| 1 | | I cannot say. I just gave a look at SQL-92 and SQL-99 BNF Grammars and the "WHERE NULL" clause is not a valid <boolean value expression>, nor the "WHERE FALSE" clause. However, by looking at the SQL-99 standard (SQL/Foundation ISO/IEC 9075-2:1999, section 4.6 Boolean types), NULL is the third boolean value for the state "UNKNOWN", and "every SQL <predicate>, <search condition>, and <boolean value expression> may be considered as an operator that returns a boolean result." (section 4.6.2.2). |
| | 1 | I cannot say. I just gave a look at SQL-92 and SQL-99 BNF Grammars and the "WHERE NULL" clause does not appear to be valid, nor the "WHERE FALSE" clause. (see http://savage.net.au/SQL/sql-99.bnf.html#where%20clause) |
| | 2 | |
| | 3 | However, by looking at the SQL-99 standard (SQL/Foundation ISO/IEC 9075-2:1999, section 4.6 Boolean types), NULL is the third boolean value for the state "UNKNOWN", and "every SQL <predicate>, <search condition>, and <boolean value expression> may be considered as an operator that returns a boolean result." (section 4.6.2.2). |
