Is there any way to get a datetime when the row was created? Is it stored anywhere? I just forgot to add a column which tells when the row was inserted, and lots of rows have been inserted and I don't know when they were inserted... Thanks.
Unfortunately there's no way to achieve that. MySQL doesn't store a timestamp of row creation, that's why you always have to create a column to do that, along with ON UPDATE clause which will update the column every time the row is updated
Nope. You need a column to record that, it's not stored in the system otherwise.
There isn't a way to get timestamp when the row was created unless you add a field that is populated with system time or has a default value.
Related
I am using conditional split to check if a row has changed or new. If new row insert it into Destination table or if existing row has been modified, update the same row.
New Rows ---ISNULL(Dest_EmpId)
Changed Rows (Id !=Dest_EmpId)||ISNULL(admin)
I have an existing column(admin) which is null and has been updated with a value (20200901). the conditional split is not able to evaluate it correctly, hence the unchanged row doesn't get updated.
Any help will be appreciated.
You have an OR condition on the IFF expression. With limited knowledge of the data that you are using and the design of the package in general, I would say that this is the only plausible explanation. Did you try changing the OR to AND and see if that helped?
Is it possible to use the id of a newly inserted row inside the rows own column as a value in a simple way?
Or do I need to Insert it first, then then get lastInsertId, and then update the row?
There is no way to do that, you would need to do as you suggest and update the row again.
See: https://dev.mysql.com/doc/refman/5.6/en/information-functions.html#function_last-insert-id
I would note, however, that this is probably a bad idea.
Is there any built in metadata in mysql that I could query to find out when a row was created if I haven't implemented that myself?
Thanks in advance.
No there is no such way by which you can detect that. You have to create a timestamp field which will store the value of the row created.
The reason why MYSQL does not keep a track of the timestamp of the row in the metadata is because that would increase the general size of the table by 4 bytes per row.
I wanna get last date when i make change in tables something like update add remove so not last modify date that table structure have been changed!
is there any way to catch this?
There is a way. But involves either writing a trigger to insert information into a "log table", or adding a last_update_time column to your table and keeping it up to date always. There is no automatic way of doing it.
I am using mysql. Now I want to write that query in which i will give mysql the row number then mysql will data from that column no only.
means..
if i have twenty rows in database but i want to get only 10th no of rows data? so how to write that kind query?
Create an INT field named "ID" that is set to "Auto Increment." This way each row will have a unique ID that you can use to select it. Details about how to do this are located here.
Add a column with the AUTO_INCREMENT flag on it, so that this columns contains the row number for all your rows. MySQL does not really have support for fetching a row by number, only by column value.