I have a table with a column of type timestamp which defaults current_timestamp and updates to current_timestamp on every update.
I want to remove the "on update" feature on this column. How do I write the alter statement?
I tried the following:
ALTER TABLE mytable alter column time set DEFAULT now();
but this didn't work.
Pete was almost correct but used the wrong syntax for 'change':
ALTER TABLE mytable CHANGE `time` `time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
Notice that you must repeat the column name. Also, make sure you are using backticks instead of single quotes to escape the column name time, which prevents it from being interpreted as the mysql column type of time.
By specifying the DEFAULT of CURRENT_TIMESTAMP, MySQL will no longer automatically update the column. From the MySQL Manual:
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.
You can't AFAIK use functions such as NOW() as a default.
Try
ALTER TABLE `mytable` CHANGE `time` `time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
(Edited to add escaping and second use of field name)
Related
I need to alter a column with timestamp datatype. The thing is when record is inserted the current time stamp should be inserted in that column. I know there is ON UPDATE CURRENT_TIMESTAMP but for insertion i can't find a way.
What you're looking for is the DEFAULT keyword.
ALTER TABLE yourTable MODIFY COLUMN yourColumn timestamp DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
What Rock 'Em wanted was to be told to use CURRENT_TIMESTAMP as the default for the column. Not on update. I use this all of the time. That way when a record gets inserted you know exactly when it happened. It is good practice in many tables to do this for audit tracking, etc.
Simply use DEFAULT clause, ignoring ON UPDATE clause, that's it should work for you!
ALTER TABLE yourTable MODIFY COLUMN yourColumn timestamp DEFAULT CURRENT_TIMESTAMP
I have a Timestamp columnn in a MySQL table. The default value of this column is CURRENT_TIMESTAMP, I want to make the ON UPDATE property of this column also equal to CURRENT_TIMESTAMP without having to drop and re-add the column, as this would cause me to lose all of the data.
Is this possible?
You ought to be able to do this successfully with an ALTER statement:
ALTER TABLE yourtable
MODIFY the_timestamp_column TIMESTAMP
DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP;
It works correctly in my quick testing.
The code below doesn't seem to work even though the collumn and table does exist, any ideas?
ALTER TABLE `table` CHANGE 'collumn_1' 'collumn_1' TIMESTAMP DEFAULT 'CURRENT_TIMESTAMP' NOT NULL
I'm just trying to make the collumn available so it can store the current date and time when any data is added to this table.
ALTER TABLE `table` MODIFY collumn_1 TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL;
I have a table with two timestamp fields. I simply defined them with a name and the type TIMESTAMP, yet for some reason MySQL automatically set one of them with a default value and the attribute on update CURRENT_TIMESTAMP. I was planning on having NO default value in either of the fields, but one of the fields is called "date_updated" so I suppose I could set the mentioned attribute to that field.
Unfortunately, it's the field "date_created" that was set with the on update CURRENT_TIMESTAMP attribute, and no matter what I do, MySQL won't let me remove it.
I've tried editing the "date_created" field and removing the attribute. When clicking save, the attribute is back. I have also tried selecting both fields, removing the attribute from one of them and setting it on the other. It gives me the error #1293 - Incorrect table definition; there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause and suddenly both attribute columns on the values are set to on update CURRENT_TIMESTAMP the result:
Error
SQL query:
ALTER TABLE `pages` CHANGE `date_created` `date_created` TIMESTAMP NOT NULL ,
CHANGE `date_updated` `date_updated` TIMESTAMP ON UPDATE CURRENT_TIMESTAMP NOT NULL
MySQL said:
#1293 - Incorrect table definition; there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause
Must I really recreate both those columns in the correct order to fix this?
I would like to know how I could solve this problem correctly, for future reference.
Thanks
Now I've also tried to run
ALTER TABLE pages
CHANGE date_created
date_created TIMESTAMP NOT NULL
You should specify DEFAULT CURRENT_TIMESTAMP (or DEFAULT 0)
ALTER TABLE pages CHANGE date_created date_created TIMESTAMP NOT NULL DEFAULT 0,
CHANGE `date_updated` `date_updated` TIMESTAMP ON UPDATE CURRENT_TIMESTAMP NOT NULL
As of MySQL version 5.6.6, you can use the explicit_defaults_for_timestamp option in the configuration file, therefore timestamp columns will not have 'DEFAULT CURRENT_TIMESTAMP' or 'ON UPDATE CURRENT_TIMESTAMP' attributes by default. It will also be possible so set these columns to NULL if they are not declared as NOT NULL.
See: http://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_explicit_defaults_for_timestamp
I am trying to set my columns default date time to system datetime.
It shows me an error
Invalid default value for
'InsertionDate'
alter table `vts`.`tblpickpoint`
add column `InsertionDate`
datetime DEFAULT 'Now()' NULL after `PickPointLatLong`
The default value for a column in mysql cannot be the result of a function.
The one exception is the current_timestamp as astander points out.
Your statement should be
alter table `vts`.`tblpickpoint`
add column `InsertionDate` TIMESTAMP
DEFAULT CURRENT_TIMESTAMP
Have a look at CURRENT_TIMESTAMP
If you want to init and update the value on every change, use this:
alter table `vts`.`tblpickpoint`
add column `InsertionDate`
TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
after `PickPointLatLong`
If you only want the creation time, use this:
alter table `vts`.`tblpickpoint`
add column `InsertionDate`
TIMESTAMP DEFAULT CURRENT_TIMESTAMP
after `PickPointLatLong`