I want add a updated_at column for every table.
The column will update its value with current time when the row is updated.
How can I automatic update it's value to avoid writing verbose code?
Thanks
You can do that directly in the database, don't need to modify your Slick code. you can define it like this, then it will automatically update whenever any value of this row is modified:
alter table xx add column updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
(this works mysql, not sure if needs adjustment for other databases)
Related
I have a PostgresSQL table that has a Date column of type TEXT
Values look like this: 2019-07-19 00:00
I want to either cast this column to type DATE so I can query based on latest values, etc.... or create a new column of type DATE and cast into there (so I have both for the future). I would appreciate any advice on both options!
Hope this isn't a dupe, but I havn't found any answers on SO.
Some context, I will need to add more data later on to the table that only has the TEXT column, which is why i want to keep the original but open to suggestions.
You can alter the column type with the simple command:
alter table my_table alter my_col type date using my_col::date
This seems to be the best solution as maintaining duplicate columns of different types is a potential source of future trouble.
Note that all values in the column have to be null or be recognizable by Postgres as a date, otherwise the conversion will fail.
Test it in db<>fiddle.
However, if you insist on creating a new column, use the update command:
alter table my_table add my_date_col date;
update my_table
set my_date_col = my_col::date;
Db<>fiddle.
Is it possible to update a column (automatically) with "current_timestamp" in PostgreSQL using "Generated Columns", whenever the row gets update?
At present, I am using trigger to update the audit field last_update_date. But I am planning to switch to generated column
ALTER TABLE test ADD COLUMN last_update_date timestamp without time zone
GENERATED ALWAYS AS (current_timestamp) STORED;
Getting error while altering column
ERROR: generation expression is not immutable
No, that won't work, for the reason specified in the error.
Functions used in generated columns must always return the same value for the same arguments, that is, depend on nothing but the current database row. current_timestamp obviously is not of that kind.
If PostgreSQL did allow such functions to be used in generated columns, then the value of the column would change if the database is restored from a pg_dump, for example.
Use a BEFORE INSERT OR UPDATE trigger for this purpose.
In PostgreSQL, is there a way to add columns that will automatically record the creation date and latest updated date of a row?
for table creation date look to event triggers
for insertion look into DEFAULT value for timestamptz column (works only if you don't explicitly define value)
for last modification, use trigger FOR EACH ROW before DELETE/UPDATE
The idea - Robust way of adding created and modified fields for data we add to database through db triggers
Update modified_by and modeified_on or modified_at for every db transaction.
Pick created_on and created_by or created_at from modified details whenever you insert a row into tables.
For trigger function, check this repo https://github.com/charan4ks/created_fields.git
I have a Column UPDATE_TIME
having the expression
TIMESTAMP NOT NULL GENERATED ALWAYS FOR EACH ROW ON UPDATE AS ROW CHANGE TIMESTAMP
how to remove the Generated always for Timestamps
I also tried
db2 "alter table xxxx alter column UPDATE_TIME drop expression"
Since it is defined as a ROW CHANGE TIMESTAMP
You have to drop the column and re-add it.
Why would you want to do this in the first place?
I am using SQL Server 2012. I need to track all the rows that were updates (as part of any action) made on a table.
I thought to add a new column (Column Name: "LastUpdated" of type Datetime.) to the table that I want to track. I would like to update the LastUpdated value every time an update is made to that row. Is there a specific way to acheive this task?
You could create a trigger. Like this:
CREATE TRIGGER dbo.Table1_Updated
ON dbo.Table1
FOR UPDATE /* Fire this trigger when a row is UPDATEd */
AS BEGIN
UPDATE dbo.Table1 SET dbo.Table1.LastUpdated = GETDATE()
FROM INSERTED
WHERE inserted.id=Table1.id
END
However, this trigger will not store WHAT was updated. Also keep in mind that if two people update it, you will only have the date of the most recent update (not all updates).
To keep a history on all changes, you might want to create an audit table (nearly identical structure to your existing table) and use a trigger to copy the pre-update data into the audit table.
This SO article talks about a solid approach: Using table auditing in order to have "snapshots" of table
You would want to look into creating a trigger to fire on update
Create TRIGGER Trigger_Name ON Table_Name
FOR update
AS
BEGIN
// update lastupdated column of updated record with current date and or time
END
Alliteratively you could just pass the new value for lastupdated when updating the other fields
We have implemented a system similar to the following:
Add a new column to your table LastUpdatedDate with a datatype of datetime
If needed, add another column with LastUpdatedBy with a datatype of varchar(100) or whatever length you need
This will store both the date/time and who performed the update.
Then when you update the row in the table, you will include those two columns in your update statement similar to this:
update yourtable
set yourCol = 'newValue',
LastUpdatedDate = getdate(),
LastUpdatedBy = 'yourUserIdentifier'