1drop table if exists t1; 2set @@session.sql_auto_is_null=1; 3select {fn length("hello")}, { date "1997-10-20" }; 4{fn length("hello")} 1997-10-20 55 1997-10-20 6create table t1 (a int not null auto_increment,b int not null,primary key (a,b)); 7insert into t1 SET A=NULL,B=1; 8insert into t1 SET a=null,b=2; 9select * from t1 where a is null and b=2; 10a b 11select * from t1 where a is null; 12a b 132 2 14explain select * from t1 where b is null; 15id select_type table type possible_keys key key_len ref rows Extra 161 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE 17drop table t1; 18CREATE TABLE t1 (a INT AUTO_INCREMENT PRIMARY KEY); 19INSERT INTO t1 VALUES (NULL); 20SELECT sql_no_cache a, last_insert_id() FROM t1 WHERE a IS NULL; 21a last_insert_id() 221 1 23SELECT sql_no_cache a, last_insert_id() FROM t1 WHERE a IS NULL; 24a last_insert_id() 25SELECT sql_no_cache a, last_insert_id() FROM t1; 26a last_insert_id() 271 1 28DROP TABLE t1; 29set @@session.sql_auto_is_null=default; 30