MySQL: Automatic Initialization and Updating for TIMESTAMP and DATETIME

 

 

https://dev.mysql.com/doc/refman/8.0/en/timestamp-initialization.html

 

1. CREATE TABLE t1 (
       ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
       dt DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
   )

   

    

    

    

    

2. CREATE TABLE t1 (
     ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     dt DATETIME DEFAULT CURRENT_TIMESTAMP
   );

    

   CREATE TABLE t1 (
       ts TIMESTAMP DEFAULT 0,
       dt DATETIME DEFAULT 0
   )

   

    

    

   

   CREATE TABLE t1 (
     ts TIMESTAMP DEFAULT 0 ON UPDATE CURRENT_TIMESTAMP,
     dt DATETIME DEFAULT 0 ON UPDATE CURRENT_TIMESTAMP
   );

    

3. TIMESTAMP & DATETIME 默认值
   

    

   CREATE TABLE t1 (
     ts1 TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,          -- default NULL
     ts2 TIMESTAMP NULL ON UPDATE CURRENT_TIMESTAMP,     -- default NULL
     ts3 TIMESTAMP NOT NULL ON UPDATE CURRENT_TIMESTAMP, -- 必须插入值
     dt1 DATETIME ON UPDATE CURRENT_TIMESTAMP,           -- default NULL
     dt2 DATETIME NULL ON UPDATE CURRENT_TIMESTAMP,      -- default NULL
     dt3 DATETIME NOT NULL ON UPDATE CURRENT_TIMESTAMP   -- 必须插入值
   );

   

    

    

    

    

    

    

    

    

4. explicit_defaults_for_timestamp
   

    

    

5.