I have a query with a limit and an offset. For example:
select * from tbl
limit 10 offset 100;
How to keep track of the count of the records, without running a second query like:
select count(*) from tbl;
I think this answers my question, but I need it for PostgreSQL. Any ideas?
I have found a solution and I want to share it. What I do is - I create a temp table from my real table with the filters applied, then I select from the temp table with a limit and offset (no limitations, so the performance is good), then select count(*) from the temp table (again no filters), then the other stuff I need and last - I drop the temp table.
select * into tmp_tbl from tbl where [limitations];
select * from tmp_tbl offset 10 limit 10;
select count(*) from tmp_tbl;
select other_stuff from tmp_tbl;
drop table tmp_tbl;
I haven't tried this, but from the section titled Obtaining the Result Status in the documentation you can use the GET DIAGNOSTICS command to determine the effect of a command.
GET DIAGNOSTICS number_of_rows = ROW_COUNT;
From the documentation:
This command allows retrieval of system status indicators. Each item is a key word identifying a state value to be assigned to the specified variable (which should be of the right data type to receive it). The currently available status items are ROW_COUNT, the number of rows processed by the last SQL command sent down to the SQL engine, and RESULT_OID, the OID of the last row inserted by the most recent SQL command. Note that RESULT_OID is only useful after an INSERT command into a table containing OIDs.
Depends if you need it from the psql CLI or if you're accessing the database from something like an HTTP server. I am using postgres from my Node server with node-postgres. The result set is returned as an array called 'rows' on the result object so I can just do
console.log(results.rows.length)
To get the row count.
ORDER BYclause.