Counting Rows

• How to find the number of rows in a table:

ANALYZE t1;
or..
VACUUM t1;
or..
REINDEX TABLE t1;
then..
SELECT reltuples FROM pg_class WHERE relname = 't1';

SELECT COUNT(*) FROM t2;


If you know the maximum value of an integer column and have an index on it:

SELECT COUNT(*) FROM t2 WHERE c2 < 1000000;


If you need to know if a table has a certain number of rows:

SELECT CASE WHEN EXISTS (SELECT 1 FROM t2 OFFSET 1000 LIMIT 1) THEN 'Yes' ELSE 'No' END;

End of presentation

This is where the actual presentation ended. Comments and questions are welcome to greg at turnstep dot com. The final few pages are just some games I put in for fun.

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