When I append,
ON UPDATE CURRENT_TIMESTAMP
I know the column will be updated when the row is updated.
Is there any way to make the clause optional?
I mean a way to update the column only when client didn't send the column value.
Use trigger logic:
CREATE TRIGGER tr
BEFORE UPDATE
ON tablename
FOR EACH ROW
SET NEW.datetimefield = COALESCE(NEW.datetimefield, CURRENT_TIMESTAMP);
Do not forget to remove ON UPDATE attribute from field definition.
One simple way to handle your requirement would be to always include the timestamp column in question in the update, but wrap it in COALESCE and use CURRENT_TIMESTAMP as the default value, e.g.
UPDATE yourTable
SET
col1 = <some value>,
co2l = <some other value>,
ts_col = COALESCE(?, CURRENT_TIMESTAMP)
WHERE ...
To the ? placeholder, you would either bind a value, should you want to explicitly update it, or just bind NULL if you don't want to update it. The NULL value would be replaced with the current timestamp.
Related
If I have a column in a table of type TIMESTAMP and has as default: CURRENT_TIMESTAMP does this column get updated to the current timestamp if I update the value
of any other column in the the same row?
It seems that it does not but I am not sure if this is what should happen.
I can not understand what this means (from MySQL documentation):
If the column is auto-updated, it is automatically updated to the
current timestamp when the value of any other column in the row is
changed from its current value. The column remains unchanged if all
other columns are set to their current values. To prevent the column
from updating when other columns change, explicitly set it to its
current value. To update the column even when other columns do not
change, explicitly set it to the value it should have]2
Give the command SHOW CREATE TABLE whatever
Then look at the table definition.
It probably has a line like this
logtime TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
in it. DEFAULT CURRENT_TIMESTAMP means that any INSERT without an explicit time stamp setting uses the current time. Likewise, ON UPDATE CURRENT_TIMESTAMP means that any update without an explicit timestamp results in an update to the current timestamp value.
You can control this default behavior when creating your table.
Or, if the timestamp column wasn't created correctly in the first place, you can change it.
ALTER TABLE whatevertable
CHANGE whatevercolumn
whatevercolumn TIMESTAMP NOT NULL
DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP;
This will cause both INSERT and UPDATE operations on the table automatically to update your timestamp column. If you want to update whatevertable without changing the timestamp, that is,
To prevent the column from updating when other columns change
then you need to issue this kind of update.
UPDATE whatevertable
SET something = 'newvalue',
whatevercolumn = whatevercolumn
WHERE someindex = 'indexvalue'
This works with TIMESTAMP and DATETIME columns. (Prior to MySQL version 5.6.5 it only worked with TIMESTAMPs) When you use TIMESTAMPs, time zones are accounted for: on a correctly configured server machine, those values are always stored in UTC and translated to local time upon retrieval.
I think you have to define the timestamp column like this
CREATE TABLE t1
(
ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);
See here
An auto-updated column is automatically updated to the current timestamp when the value of any other column in the row is changed from its current value. An auto-updated column remains unchanged if all other columns are set to their current values.
To explain it let's imagine you have only one row:
-------------------------------
| price | updated_at |
-------------------------------
| 2 | 2018-02-26 16:16:17 |
-------------------------------
Now, if you run the following update column:
update my_table
set price = 2
it will not change the value of updated_at, since price value wasn't actually changed (it was already 2).
But if you have another row with price value other than 2, then the updated_at value of that row (with price <> 3) will be updated to CURRENT_TIMESTAMP.
Add a trigger in database:
DELIMITER //
CREATE TRIGGER update_user_password
BEFORE UPDATE ON users
FOR EACH ROW
BEGIN
IF OLD.password <> NEW.password THEN
SET NEW.password_changed_on = NOW();
END IF;
END //
DELIMITER ;
The password changed time will update only when password column is changed.
Adding where to find UPDATE CURRENT_TIMESTAMP because for new people this is a confusion.
Most people will use phpmyadmin or something like it.
Default value you select CURRENT_TIMESTAMP
Attributes (a different drop down) you select UPDATE CURRENT_TIMESTAMP
If I have a column in a table of type TIMESTAMP and has as default: CURRENT_TIMESTAMP does this column get updated to the current timestamp if I update the value
of any other column in the the same row?
It seems that it does not but I am not sure if this is what should happen.
I can not understand what this means (from MySQL documentation):
If the column is auto-updated, it is automatically updated to the
current timestamp when the value of any other column in the row is
changed from its current value. The column remains unchanged if all
other columns are set to their current values. To prevent the column
from updating when other columns change, explicitly set it to its
current value. To update the column even when other columns do not
change, explicitly set it to the value it should have]2
Give the command SHOW CREATE TABLE whatever
Then look at the table definition.
It probably has a line like this
logtime TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
in it. DEFAULT CURRENT_TIMESTAMP means that any INSERT without an explicit time stamp setting uses the current time. Likewise, ON UPDATE CURRENT_TIMESTAMP means that any update without an explicit timestamp results in an update to the current timestamp value.
You can control this default behavior when creating your table.
Or, if the timestamp column wasn't created correctly in the first place, you can change it.
ALTER TABLE whatevertable
CHANGE whatevercolumn
whatevercolumn TIMESTAMP NOT NULL
DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP;
This will cause both INSERT and UPDATE operations on the table automatically to update your timestamp column. If you want to update whatevertable without changing the timestamp, that is,
To prevent the column from updating when other columns change
then you need to issue this kind of update.
UPDATE whatevertable
SET something = 'newvalue',
whatevercolumn = whatevercolumn
WHERE someindex = 'indexvalue'
This works with TIMESTAMP and DATETIME columns. (Prior to MySQL version 5.6.5 it only worked with TIMESTAMPs) When you use TIMESTAMPs, time zones are accounted for: on a correctly configured server machine, those values are always stored in UTC and translated to local time upon retrieval.
I think you have to define the timestamp column like this
CREATE TABLE t1
(
ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);
See here
An auto-updated column is automatically updated to the current timestamp when the value of any other column in the row is changed from its current value. An auto-updated column remains unchanged if all other columns are set to their current values.
To explain it let's imagine you have only one row:
-------------------------------
| price | updated_at |
-------------------------------
| 2 | 2018-02-26 16:16:17 |
-------------------------------
Now, if you run the following update column:
update my_table
set price = 2
it will not change the value of updated_at, since price value wasn't actually changed (it was already 2).
But if you have another row with price value other than 2, then the updated_at value of that row (with price <> 3) will be updated to CURRENT_TIMESTAMP.
Add a trigger in database:
DELIMITER //
CREATE TRIGGER update_user_password
BEFORE UPDATE ON users
FOR EACH ROW
BEGIN
IF OLD.password <> NEW.password THEN
SET NEW.password_changed_on = NOW();
END IF;
END //
DELIMITER ;
The password changed time will update only when password column is changed.
Adding where to find UPDATE CURRENT_TIMESTAMP because for new people this is a confusion.
Most people will use phpmyadmin or something like it.
Default value you select CURRENT_TIMESTAMP
Attributes (a different drop down) you select UPDATE CURRENT_TIMESTAMP
If I have a column in a table of type TIMESTAMP and has as default: CURRENT_TIMESTAMP does this column get updated to the current timestamp if I update the value
of any other column in the the same row?
It seems that it does not but I am not sure if this is what should happen.
I can not understand what this means (from MySQL documentation):
If the column is auto-updated, it is automatically updated to the
current timestamp when the value of any other column in the row is
changed from its current value. The column remains unchanged if all
other columns are set to their current values. To prevent the column
from updating when other columns change, explicitly set it to its
current value. To update the column even when other columns do not
change, explicitly set it to the value it should have]2
Give the command SHOW CREATE TABLE whatever
Then look at the table definition.
It probably has a line like this
logtime TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
in it. DEFAULT CURRENT_TIMESTAMP means that any INSERT without an explicit time stamp setting uses the current time. Likewise, ON UPDATE CURRENT_TIMESTAMP means that any update without an explicit timestamp results in an update to the current timestamp value.
You can control this default behavior when creating your table.
Or, if the timestamp column wasn't created correctly in the first place, you can change it.
ALTER TABLE whatevertable
CHANGE whatevercolumn
whatevercolumn TIMESTAMP NOT NULL
DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP;
This will cause both INSERT and UPDATE operations on the table automatically to update your timestamp column. If you want to update whatevertable without changing the timestamp, that is,
To prevent the column from updating when other columns change
then you need to issue this kind of update.
UPDATE whatevertable
SET something = 'newvalue',
whatevercolumn = whatevercolumn
WHERE someindex = 'indexvalue'
This works with TIMESTAMP and DATETIME columns. (Prior to MySQL version 5.6.5 it only worked with TIMESTAMPs) When you use TIMESTAMPs, time zones are accounted for: on a correctly configured server machine, those values are always stored in UTC and translated to local time upon retrieval.
I think you have to define the timestamp column like this
CREATE TABLE t1
(
ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);
See here
An auto-updated column is automatically updated to the current timestamp when the value of any other column in the row is changed from its current value. An auto-updated column remains unchanged if all other columns are set to their current values.
To explain it let's imagine you have only one row:
-------------------------------
| price | updated_at |
-------------------------------
| 2 | 2018-02-26 16:16:17 |
-------------------------------
Now, if you run the following update column:
update my_table
set price = 2
it will not change the value of updated_at, since price value wasn't actually changed (it was already 2).
But if you have another row with price value other than 2, then the updated_at value of that row (with price <> 3) will be updated to CURRENT_TIMESTAMP.
Add a trigger in database:
DELIMITER //
CREATE TRIGGER update_user_password
BEFORE UPDATE ON users
FOR EACH ROW
BEGIN
IF OLD.password <> NEW.password THEN
SET NEW.password_changed_on = NOW();
END IF;
END //
DELIMITER ;
The password changed time will update only when password column is changed.
Adding where to find UPDATE CURRENT_TIMESTAMP because for new people this is a confusion.
Most people will use phpmyadmin or something like it.
Default value you select CURRENT_TIMESTAMP
Attributes (a different drop down) you select UPDATE CURRENT_TIMESTAMP
Is it possible to update zero columns in a MySQL update query?
I'd like to utilise the automatic updating of the timestamp column when this particular row is selected. Does anyone have any clue?
So you want your update query to only update the timestamp column? Just update it yourself instead of relying on the automatic update:
UPDATE mytable SET tscolumn = NOW() WHERE ...
Just try something like :
UPDATE myTable SET someField = someField WHERE id = myId
So the data values won't move, and the automatic timestamp will be updated.
As said by GaryG, you may also update the timestamp directly.
I want to create a table with two column, one "created" and one "modified", with a timestamp type. I don't want them to have a default value. But when I create them, it automatically puts CURRENT_TIMESTAMP as default for at least one of them, and also on update.
How can I just have type timestamp with no default or on update value for any of my column?
Edit: I use MySQL
If you are using SQL Server, the timestamp type is used for row versioning, not for storing an actual date or time value. See MSDN.
You could create the columns with a datetime datatype and then set your created and modified values with triggers.
CREATE TRIGGER trg_SetDateCreated ON MyTable
FOR INSERT AS
UPDATE MyTable
SET created = CURRENT_TIMESTAMP
WHERE MyTable.id = (SELECT Id FROM Inserted);
GO
CREATE TRIGGER trg_SetDateModified ON MyTable
FOR UPDATE AS
UPDATE MyTable
SET modified = CURRENT_TIMESTAMP
WHERE MyTable.id = (SELECT Id FROM Inserted);
GO