Description:
I get a different timestamp value about null in the same environment！
How to repeat:
mysql> select version() \G
*************************** 1. row ***************************
version(): 5.7.12-log
1 row in set (0.00 sec)
mysql> create table tab1(name varchar(8) default null) engine = innodb default charset=utf8;
Query OK, 0 rows affected (0.01 sec)
mysql> create table tab2(name varchar(8) default 'test') engine = innodb default charset=utf8;
Query OK, 0 rows affected (0.02 sec)
mysql> insert into tab1 values(null);
Query OK, 1 row affected (0.00 sec)
mysql> insert into tab2 values(null);
Query OK, 1 row affected (0.00 sec)
mysql> update tab1 set name=null;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
mysql> update tab2 set name=null;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
mysql> create table tab_timestamp1(name varchar(8) default null,gmt_modify timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP)engine = innodb default charset=utf8;
Query OK, 0 rows affected (0.01 sec)
mysql> create table tab_timestamp2(name varchar(8) default 'test',gmt_modify timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP)engine = innodb default charset=utf8;
Query OK, 0 rows affected (0.01 sec)
mysql> insert into tab_timestamp1 values(null,now());
Query OK, 1 row affected (0.00 sec)
mysql> insert into tab_timestamp2 values(null,now());
Query OK, 1 row affected (0.01 sec)
mysql> update tab_timestamp1 set name = null;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
mysql> update tab_timestamp2 set name = null;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
Suggested fix:
I get a different timestamp value about null in the same environment！
