在MySQL 5.6.6之前，TIMESTAMP的默認(rèn)行為：

• TIMESTAMP列如果沒(méi)有明確聲明NULL屬性，默認(rèn)為NOT NULL。（而其他數(shù)據(jù)類型，如果沒(méi)有顯示聲明為NOT NULL，則允許NULL值。）設(shè)置TIMESTAMP的列值為NULL，會(huì)自動(dòng)存儲(chǔ)為當(dāng)前timestamp。
• 表中的第一個(gè)TIMESTAMP列，如果沒(méi)有聲明NULL屬性、DEFAULT或者 ON UPDATE，會(huì)自動(dòng)分配 DEFAULT CURRENT_TIMESTAMP和ON UPDATE CURRENT_TIMESTAMP 屬性。
• 表中第二個(gè)TIMESTAMP列，如果沒(méi)有聲明為NULL或者DEFAULT子句，默認(rèn)自動(dòng)分配’0000-00-00 00:00:00′。插入行時(shí)沒(méi)有指明改列的值，該列默認(rèn)分配’0000-00-00 00:00:00′，且沒(méi)有警告。

因?yàn)槟J(rèn)情況下充許為空,當(dāng)插入值時(shí),分兩種情況：第一列與第二列情況 explicit_defaults_for_timestamp=false [默認(rèn)值] mysql> create table timestamp(id int not null auto_increment,time1 timestamp,time2 timestamp,primary key(id))engine=innodb; Query OK, 0 rows affected (0.27 sec)mysql> insert into timestamp(id) values(1); Query OK, 1 row affected (0.21 sec)mysql> select * from timestamp; +----+---------------------+---------------------+ | id | time1 | time2 | +----+---------------------+---------------------+ | 1 | 2016-07-02 17:12:28 | 0000-00-00 00:00:00 | +----+---------------------+---------------------+ 1 row in set (0.19 sec)mysql> mysql> show create table timestamp;
CREATE TABLE `timestamp` (`id` int(11) NOT NULL AUTO_INCREMENT, `time1` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,`time2` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8

2列TIMESTAMP未聲明為NULL的默認(rèn)行為 timestamp有兩個(gè)屬性，分別是CURRENT_TIMESTAMP 和ON UPDATE CURRENT_TIMESTAMP兩種，使用情況分別如下：1. CURRENT_TIMESTAMP 當(dāng)要向數(shù)據(jù)庫(kù)執(zhí)行insert操作時(shí)，如果有個(gè)timestamp字段屬性設(shè)為 CURRENT_TIMESTAMP，則無(wú)論這個(gè)字段有沒(méi)有set值都插入當(dāng)前系統(tǒng)時(shí)間 2. ON UPDATE CURRENT_TIMESTAMP當(dāng)執(zhí)行update操作時(shí)，并且字段有ON UPDATE CURRENT_TIMESTAMP屬性。則字段無(wú)論值有沒(méi)有變化，它的值也會(huì)跟著更新為當(dāng)前UPDATE操作時(shí)的時(shí)間。

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從MySQL5.6.6開(kāi)始這種默認(rèn)設(shè)置的方法被廢棄了。在MySQL啟動(dòng)時(shí)會(huì)出現(xiàn)以下警告：

1 2 3

[Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (seedocumentation for more details).

關(guān)閉警告，在my.cnf中加入

1 2	[mysqld] explicit_defaults_for_timestamp=true

重啟MySQL后錯(cuò)誤消失，這時(shí)TIMESTAMP的行為如下：

• TIMESTAMP如果沒(méi)有顯示聲明NOT NULL，是允許NULL值的，可以直接設(shè)置改列為NULL，而沒(méi)有默認(rèn)填充行為。
• TIMESTAMP不會(huì)默認(rèn)分配DEFAULT CURRENT_TIMESTAMP 和 ON UPDATE CURRENT_TIMESTAMP屬性。

mysql> create table timestamp1(id int not null auto_increment,time1 timestamp,time2 timestamp,primary key(id))engine=innodb; Query OK, 0 rows affected (0.11 sec)mysql> insert into timestamp1(id) values(1); Query OK, 1 row affected (0.18 sec)mysql> show create table timestamp1; CREATE TABLE `timestamp1` (`id` int(11) NOT NULL AUTO_INCREMENT, `time1` timestamp NULL DEFAULT NULL,`time2` timestamp NULL DEFAULT NULL,PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 mysql> select * from timestamp1; +----+-------+-------+ | id | time1 | time2 | +----+-------+-------+ | 1 | NULL | NULL | +----+-------+-------+ 1 row in set (0.18 sec)

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mysql> set sql_mode="STRICT_TRANS_TABLES"; Query OK, 0 rows affected (0.00 sec)mysql> create table timestamp4(id int not null auto_increment,time1 timestamp not null,time2 timestamp not null,primary key(id))engine=innodb; Query OK, 0 rows affected (0.03 sec) mysql> insert into timestamp4 select 1,"0000-00-00 00:00:00","0000-00-00 00:00:00"; Query OK, 1 row affected (0.17 sec) Records: 1 Duplicates: 0 Warnings: 0mysql> insert into timestamp4 select 1,"0000-00-00 00:00:00","5"; ERROR 1292 (22007): Incorrect datetime value: '5' for column 'time2' at row 1

mysql> set sql_mode="STRICT_TRANS_TABLES,NO_ZERO_DATE"; Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> insert into timestamp4 select 1,"0000-00-00 00:00:00","0000-00-00 00:00:00"; ERROR 1292 (22007): Incorrect datetime value: '0000-00-00 00:00:00' for column 'time1' at row 1 mysql> set sql_mode="STRICT_TRANS_TABLES,NO_ZERO_DATE,NO_ZERO_IN_DATE"; Query OK, 0 rows affected, 2 warnings (0.00 sec) mysql> insert into timestamp4 select 5,"2000-10-10 10:20:10","2000-10-10 10:20:00"; Query OK, 1 row affected (0.18 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> insert into timestamp4 select 7,"2000-10-00 10:20:10","2000-10-10 10:20:11"; 日期中不能有00 ERROR 1292 (22007): Incorrect datetime value: '2000-10-00 10:20:10' for column 'time1' at row 1

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mysql> create table y( a int not null auto_increment primary key,b timestamp Default CURRENT_TIMESTAMP);
當(dāng)有記錄插入時(shí),把當(dāng)前日期與時(shí)間寫入到 b字段中，但更新不會(huì)改變值 mysql> create table y1( a int not null auto_increment primary key,b timestamp on update CURRENT_TIMESTAMP);
當(dāng)有記錄插入時(shí),NULL寫入到B 字段中,當(dāng)該行update時(shí)，b列值為當(dāng)前更新時(shí)間值 mysql> create table y2( a int not null auto_increment primary key,b timestamp default current_timestamp on update CURRENT_TIMESTAMP); 當(dāng)插入時(shí),有一個(gè)默認(rèn)值,隨著當(dāng)前行的更新,b列值也隨著更新為當(dāng)前更新時(shí)間mysql> insert into y(a) values(null); Query OK, 1 row affected (0.17 sec)mysql> insert into y1(a) values(null); Query OK, 1 row affected (0.17 sec)mysql> insert into y2(a) values(null); Query OK, 1 row affected (0.17 sec)mysql> select * from y; +---+---------------------+ | a | b | +---+---------------------+ | 1 | 2016-07-02 18:56:59 | +---+---------------------+ 1 row in set (0.00 sec)mysql> select * from y1; +---+------+ | a | b | +---+------+ | 1 | NULL | +---+------+ 1 row in set (0.00 sec) mysql> select * from y2; +---+---------------------+ | a | b | +---+---------------------+ | 1 | 2016-07-02 18:57:08 | +---+---------------------+ 1 row in set (0.00 sec)




mysql> update y set a=2 where a=1; Query OK, 1 row affected (0.20 sec) Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from y; +---+---------------------+ | a | b | +---+---------------------+ | 2 | 2016-07-02 18:56:59 | +---+---------------------+ 1 row in set (0.01 sec)mysql> update y1 set a=2 where a=1; Query OK, 1 row affected (0.17 sec) Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from y1; +---+---------------------+ | a | b | +---+---------------------+ | 2 | 2016-07-02 19:00:12 | +---+---------------------+ 1 row in set (0.00 sec)mysql> update y2 set a=2 where a=1; Query OK, 1 row affected (0.01 sec) Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from y2; +---+---------------------+ | a | b | +---+---------------------+ | 2 | 2016-07-02 19:00:35 | +---+---------------------+ 1 row in set (0.00 sec) 設(shè)置正常日期格式:

嚴(yán)格日期格式:
set sql_mode="STRICT_TRANS_TABLES,NO_ZERO_DATE,NO_ZERO_IN_DATE"; 手動(dòng)指定默認(rèn)值:
create table y2( a int not null auto_increment primary key,b timestamp default current_timestamp on update CURRENT_TIMESTAMP);

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轉(zhuǎn)載于:https://www.cnblogs.com/zengkefu/p/5636593.html

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