Two MySQL timestamp columns in one table - mysql

Question

I would like to create a table that has both a column for "created" and another for "updated". The column "created" will be set at insert and never change. The column "updated" will change every time a row is updated. I don't want to mess with either of these columns in the subsequent INSERT or UPDATE statements. So what should my CREATE TABLE statement look like if I start with something like this?
CREATE TABLE IF NOT EXISTS `mydb`.`mytable` (
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`updated` TIMESTAMP,
`created` TIMESTAMP,
`deleted` TINYINT DEFAULT 0,
`notes` TEXT DEFAULT '',
`description` VARCHAR(100)
) TYPE=innodb;
I seem to be having trouble creating a table with two TIMESTAMP columns. I don't care if the columns are TIMESTAMP or DATETIME or whatever, I just want them to be populated by MySQL without explicit instructions from the insert or update statements.
I would like to be able to do inserts like this:
INSERT INTO `mydb`.`mytable` (notes,description) VALUES ('some note','some description');
and updates like this:
UPDATE `mydb`.`mytable` SET notes=CONCAT(notes,'some more notes') WHERE id=1;
both without having to explicitly set the "created" column or set (or reset) the "updated" column in the insert or update statement.

Answer 1

Try this one to create your table:
CREATE TABLE IF NOT EXISTS db.test_table
(
Id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
created DATETIME DEFAULT NULL,
updated TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
deleted TINYINT DEFAULT 0,
notes TEXT DEFAULT NULL,
description VARCHAR(100)
)
Note that
updated TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
will allow to update this field automatically.
And set this one for a trigger before inserting records:
DELIMITER $$
CREATE
/*[DEFINER = { user | CURRENT_USER }]*/
TRIGGER `db`.`on_before_insert` BEFORE INSERT
ON `db`.`test_table`
FOR EACH ROW BEGIN
SET new.created = NOW();
END$$
DELIMITER ;
Then you can use this to insert:
INSERT INTO db.test_table(description) VALUES ("Description")
and to update your record
UPDATE db.test_table SET description = "Description 2" where Id=1
And your created and updated fields will be set appropiately.

Answer 2

News flash: In mysql, TIMESTAMP columns are always updated with now() every time any other column in the row is updated - this is a deliberate feature of this datatype.
DATETIME on the other hand does not have this weird behaviour - it's completely normal.
The answer: created must be DATETIME, but due to this bug, you also need a trigger, like this:
CREATE TABLE IF NOT EXISTS mytable (
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`updated` TIMESTAMP, -- This will be updated to now(), if you don't set it or set it to null
`created` DATETIME NOT NULL, -- This will never be magically updated once written
`deleted` TINYINT DEFAULT 0,
`notes` TEXT DEFAULT '',
`description` VARCHAR(100)
) TYPE=innodb;
DELIMITER ~
CREATE TRIGGER mytable_insert_trigger
BEFORE INSERT ON mytable
FOR EACH ROW BEGIN
SET NEW.created = CURRENT_TIMESTAMP;
END;~
DELIMITER ;
insert into mytable (notes) values ('test');
select * from mytable;
+----+---------------------+---------------------+---------+-------+-------------+
| id | updated | created | deleted | notes | description |
+----+---------------------+---------------------+---------+-------+-------------+
| 1 | 2011-07-05 11:48:02 | 2011-07-05 11:48:02 | 0 | test | NULL |
+----+---------------------+---------------------+---------+-------+-------------+

Answer 3

Try this:
CREATE TABLE IF NOT EXISTS mydb.mytable
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
updated DATETIME,
created TIMESTAMP,
deleted TINYINT DEFAULT 0,
notes TEXT DEFAULT '',
description VARCHAR(100)
) TYPE=innodb;
Edit: Use a trigger.
CREATE TRIGGER mytable_update
BEFORE UPDATE ON mydb.mytable
FOR EACH ROW SET NEW.updated = NOW();

Answer 4

alternative is to change the order of timestamp column
OR
set first column DEFAULT value like this
ALTER TABLE `tblname` CHANGE `first_timestamp_column`
`first_timestamp_column` TIMESTAMP NOT NULL DEFAULT 0;
Reference

Answer 5

Unfortunately MySQL doesn't let you have two TIMESTAMP columns in one table. I would use ON UPDATE CURRENT_TIMESTAMP for the updated column and set created manually using the NOW() function.