Ilan.

ex. $sql = “SELECT id FROM users where email = ‘uniq@email.com’ LIMIT 1″;

If you’re executing count(*) queries for such result sets MySQL will perform the join even if you use LEFT JOIN so it is not needed which slows down things considerably. In similar way MySQL generates full rows while executing queries with limit befor…

While this works when performing LEFT JOINS, with INNER JOINS it’s a different thing.
Let’s say we want 10 records, starting from offset 500000, where i & 10000, like in the above example, but let’s perform an innerj join instead…
The first subquery will return the requested 10 results, and asuming in the res table there are rows that don’t match some rows returned by the subquery, then the result will be less than 10 rows…