This seems like a really simple one but I'm struggling to figure it out. I want a column in my database that lists when a record was first created and another column that says when it was updated. It's my understanding I should be able to do all this just using MySQL. All help is appreciated :)
This stinks still no answer, reasons I'm already starting to miss Ruby on Rails...
You will probably need to use a combination of the Datetime datatype and the Timestamp data type. I would set my created column as a DateTime with a DEFAULT NOW(), and my updated column as a Timestamp with DEFAULT CURRENT_TIMESTAMP and an ON UPDATE CURRENT_TIMESTAMP attribute.
Here are the docs for the Timestamp dt:
http://dev.mysql.com/doc/refman/5.0/en/timestamp.html
In a CREATE TABLE statement, the first TIMESTAMP column can be declared in any of the following ways:
With both DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP clauses, the column has the current timestamp for its default value, and is automatically updated.
With neither DEFAULT nor ON UPDATE clauses, it is the same as DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP.
With a DEFAULT CURRENT_TIMESTAMP clause and no ON UPDATE clause, the column has the current timestamp for its default value but is not automatically updated.
With no DEFAULT clause and with an ON UPDATE CURRENT_TIMESTAMP clause, the column has a default of 0 and is automatically updated.
With a constant DEFAULT value, the column has the given default and is not automatically initialized to the current timestamp. If the column also has an ON UPDATE CURRENT_TIMESTAMP clause, it is automatically updated; otherwise, it has a constant default and is not automatically updated.
To fulfill your question and for others viewing this question, here is the answer. Note this was written for MySQL 5.x.
DROP TABLE IF EXISTS `test1`;
CREATE TABLE `test1` (
`id` INT NULL AUTO_INCREMENT ,
`name` varchar(50) NOT NULL ,
`created` DATETIME ,
`updated` DATETIME ,
PRIMARY KEY (`id`),
INDEX (`name`)
);
DELIMITER $$
DROP TRIGGER IF EXISTS `test1_created`$$
CREATE TRIGGER `test1_created` BEFORE INSERT ON `test1`
FOR EACH ROW BEGIN
SET NEW.`created` = UTC_TIMESTAMP();
SET NEW.`updated` = UTC_TIMESTAMP();
END;
$$
DROP TRIGGER IF EXISTS `test1_updated`$$
CREATE TRIGGER `test1_updated` BEFORE UPDATE ON `test1`
FOR EACH ROW BEGIN
SET NEW.`updated` = UTC_TIMESTAMP();
END;
$$
DELIMITER ;
Note
You could use TIMESTAMP for the updated column which would have automatically updated the value thus not requiring the BEFORE UPDATE trigger, however TIMESTAMP has a range from 1970 to 2038 which is fast approaching and I like to think my applications will live forever :). Although TIMESTAMP is only 4bytes while DATETIME is 8bytes.
TIMESTAMP range '1970-01-01 00:00:01' UTC to '2038-01-19 03:14:07' UTC
DATETIME range '1000-01-01 00:00:00' to '9999-12-31 23:59:59'
From the MySQL 5.0 Certification Guide:
CREATE TABLE ts_test5 (
created TIMESTAMP DEFAULT 0,
updated TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
data CHAR(30)
);
To control the initialization and update behaviour of a TIMESTAMP column, you add either or both of the DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP attributes to the column defintion when creating the table with CREATE TABLE...
and
...if you do not specify either of the DEFAULT CURRENT_TIMESTAMP or ON UPDATE CURRENT_TIMESTAMP attributes when creating a table, MySQL automatically assigns BOTH to the first TIMESTAMP column
Also
you cannot use DEFAULT CURRENT_TIMESTAMP with one column and ON UPDATE CURRENT_TIMESTAMP with another
If you can't use the timestamp fields with default attributes that Paul W has suggested, you can use AFTER INSERT and AFTER UPDATE triggers to populate the fields.
You will need two fields "Created" and
"Updated" with type datetime. When a
new entry is inserted then insert
"Created" with current time stamp.
When a update is happening insert
"Updated" with the current time stamp,
and let the "Created" field remain as
it is.
For current time stamp you can use
NOW() in your mysql query.
Related
I have been making tables with a modified row which is time stamped.
`modified` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
I am seeking to rename this as bookedinand timestamp the day of entry into the database.
i have looked on the net for a solution at sites like http://www.w3schools.com/sql/func_curdate.asp
And cant seem to find a solution that works or is what i need.
I tried to edit it in the databse myself but with no luck. as you can tell im a extremity novice
Instead of w3schools you really should use the actual MySQL documentations. http://dev.mysql.com/doc/refman/5.1/en/alter-table.html
alter table tablename change `modified` `bookedin` timestamp NOT NULL DEFAULT
CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
Or maybe just
alter table tablename change `modified` `bookedin` timestamp NOT NULL DEFAULT
CURRENT_TIMESTAMP;
I think the on update may just be part of the timestamp datatype. And, I think that altering the name of the table might cause all the rows to update their timestamp to the date you did it. So you might want to make a copy of the table and try it out first. I remember running into a problem like that once that made me switch from using TIMESTAMP to DATETIME.
I'm trying to make a table that has two timestamps columns, one will be for when a row is created and the other for when the row is updated. Here's what I tried so far:
CREATE TABLE `tmp` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`data` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`created` timestamp NOT NULL ,
`modified` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
But I'm getting this error:
Incorrect table definition; there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause
You can do this in MySQL 5.6 (available at the time of writing as release candidate but not yet production-ready).
As of MySQL 5.6.5, TIMESTAMP and DATETIME columns can be automatically initializated and updated to the current date and time (that is, the current timestamp). Before 5.6.5, this is true only for TIMESTAMP, and for at most one TIMESTAMP column per table.... For any TIMESTAMP or DATETIME column in a table, you can assign the current timestamp as the default value, the auto-update value, or both
taken from https://dev.mysql.com/doc/refman/5.6/en/timestamp-initialization.html
This is a MYSQL constraint, You can have only one column whose default value will be the systime.
This question can also be referred
How to add "ON update current timestamp" to existing table column
You could write a trigger to add the created timestamp on inserts seperately
delimiter |
CREATE TRIGGER add_created_ts BEFORE INSERT on `tmp`
FOR EACH ROW
BEGIN
SET NEW.created = current_timestamp;
END
|
delimiter ;
i have a table that looks like this:
Field: msg_sent_datetime
Type: datetime
yet when i use NOW() in a php mysql insert query it is staying as all zeros?
any idea why?
If you're using it only at the time of INSERT, you could make the field a TIMESTAMP and set a default of CURRENT_TIMESTAMP.
Without knowing more about the code it's difficult to suggest much else.
Example with CURRENT_TIMESTAMP
CREATE TABLE example (
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
msg TEXT,
msg_sent_datetime TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
Also, if you want it to always update when there's a change to the row, you can add the ON UPDATE CURRENT_TIMESTAMP property to the table definition:
CREATE TABLE example (
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
msg TEXT,
msg_sent_datetime TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);
Of course, all of this is totally dependent on switching to TIMESTAMP which you may not want
I dont knw exactly why, but mysql has 2 datetime functions: now() and sysdate(). Perhaps you can substitute now() with sysdate() to help you troubleshoot.
http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_sysdate
project is written on php.
There is timestamp field in mysql it updates automatically. In one case I don`t need update this field. Can I gibe instruction not to update this field in this queries without getting timestamp value.
You should change it to DEFAULT CURRENT_TIMESTAMP otherwise it will auto-update. From the manual:
In a CREATE TABLE statement, the first TIMESTAMP column can be declared in any of the following ways:
With both DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP clauses, the column has the current timestamp for its default value, and is automatically updated.
With neither DEFAULT nor ON UPDATE clauses, it is the same as DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP.
With a DEFAULT CURRENT_TIMESTAMP clause and no ON UPDATE clause, the column has the current timestamp for its default value but is not automatically updated.
Edit the column in phpMyAdmin and unselect the option for "on update current timestamp."
I have a database table in mysql with a field that is of "TIMESTAMP" type. I need help writing the SQL query to update the field with the current timestamp.
UPDATE tb_Test set dt_modified = ?????
Use:
UPDATE tb_Test
SET dt_modified = CURRENT_TIMESTAMP
WHERE ? -- if you don't specify, ALL dt_modified values will be updated
You can use NOW() instead of CURRENT_TIMESTAMP, but CURRENT_TIMESTAMP is ANSI standard so the query can be ported to other databases.
ALTER TABLE tb_Test MODIFY COLUMN dt_modified TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
Now whenever any field is changed the dt_modified will be updated by the special trigger.