How can we trigger a mysql trigger when the system date is changed? Let's say
We have a mysql table and it has a dateTime column and at a specific time of each day we need to update that dateTime column according to a specific condition. So is it possible to achieve this task in mysql?
How can we trigger a mysql trigger when the system date is changed?
You cannot create this trigger. There are only table INSERT/UPDATE/DELETE triggers.
One more thing - as I know, the MySQL server should be restarted after system date changing.
Related
I am running MySQL 5.6. I want to know which row/rows have been updated in a table. One way is to create a trigger using PHPMyAdmin. This trigger can store row id (id is be a table column) of that row and current datetime into another table. This way I will know which record has changed. In PhpMyAdmin when I add trigger it asks me event, time and table which I filled. But what do I write in Definition & Definer.
I am trying to create a table that includes a column that contains just the current date-not timestamp-using the MariaDB base. Which is the command that sets the content of the column as the current date upon table creation?
Why on table create, as there will be no data, if you need a date and not datetime add to code, WELL before adding a trigger, keep business logic at the business layer not at storage layer.
Not your exact answer to the specific question but hopefully helpful advice, btw I don’t like triggers, so am a bit biased
MariaDB introduced DEFAULTs for DATETIME in 10.0.1.
See worklog . It is patterned after the MySQL 5.6.5 feature , which has examples.
If you want to default to only CURDATE(), I think you are out of luck in MariaDB and MySQL.
A BEFORE INSERT TRIGGER with SET NEW.datetime_col = CURDATE() should give you the functionality:
CREATE TRIGGER set_date BEFORE INSERT ON tbl
FOR EACH ROW SET NEW.datetime_col = CURDATE();
So I have timestamp column in table that I wanted to update every time that row is accessed, including INSERT, SELECT & UPDATE statements.
(Note that not just when the row is modified)
Is there built-in feature for MySQL to achieve this?
There is a feature that does this! In MySQL they are called Triggers. With Triggers you can run additional MySQL code when performing an action (i.e.: when INSERTING, SELECTING, UPDATING, DELETING, etc. a table).
For example, the data is like this:
[id][name]
at 10:00, the data is like this:
[1][John]
at 11:00, the user edit the data change to this:
[1][Johnson]
So, user use the alter command to change the data, but it is possible for the database query back the data on 10:00 in MySQL? Thanks.
What you are talking about is versioning. Having time stamp and version number would help but storing multiple records in same table with same id would cause a decrease in data integrity - what about a trigger on the table and insert into some form of audit table?
In general you have two options:
Add a colum version with a timestamp and expand the primary key to your currient PK and the version. To grep the data you just need to select the least version e.g. with max. Or add another colum with a bit value for the newest version. This should be faster to select.
Create a table with historical values. To implement this you need to add a trigger to the orginal table on update and copy the old value in your history table. So you can see all changes.
I haver zero experience with triggers in MySQL. Learnt them in school (Oracle environment).
I have a table which already has a datestamp column for insert date.
I want to update a Record_Touched field whenever any record is touched in this table. What is the best efficient way of doing it?
Thank you...
Create that field as a TimeStamp and set ON UPDATE CURRENT_TIMESTAMP
As described, I do not believe that you need a Trigger.