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How to return affected row count in PostgreSQL?
Depending on what you might want to achieve, the special boolean variable “FOUND” could serve; UPDATE, INSERT, and DELETE statements set FOUND true if at least one row is affected, false if no row is affected. Thanks for contributing an answer to Stack Overflow!
Why is the count function slow in PostgreSQL?
When you apply the COUNT (*) function to the entire table, PostgreSQL has to scan the whole table sequentially. If you use the COUNT (*) function on a big table, the query will be slow. This is related to the PostgreSQL MVCC implementation.
How to calculate the number of payments in PostgreSQL?
PostgreSQL COUNT() with GROUP BY clause To get the number of payments by the customer, you use the GROUP BY clause to group the payments into groups based on customer id, and use the COUNT() function to count the payments for each group.
How to select count of rows in another table?
I think the comment by @intgr in another answer is so valuable I’m putting forward this as an alternate answer as this method allows you to filter the calculated column efficiently.
When to use update statement in PostgreSQL?
In other words: Use UPDATE RETURNING, either directly to produce the calculated rows, or in a writeable CTE for more complex cases. Generally the answer to this question depends on the type of the driver used.
What happens if no row is returned in plpgsql?
If no row is returned then we know that there was a previous update and the client may need to refresh the data before trying to update clause again. This is why we need to know how many rows where affected by the update statement before returning computed columns. No row should be returned if the update fails.
How to get affected rows by update statement in raw SQL?
This has been asked multiple times here and here, but none of the answers are suitable in my case because I do not want to execute my update statement in a PL/PgSQL function and use GET DIAGNOSTICS integer_var = ROW_COUNT. I have to do this in raw SQL. For instance, in MS SQL SERVER we have @@ROWCOUNT which could be used like the following :