Does Limiting A Query To One Record Improve Performance
Will limiting a query to one result record, improve performance in a large(ish) MySQL table if the table only has one matching result?
select * from people where name = "Re0sless" limit 1
if there is only one record with that name? and what about if
name was the primary key/ set to unique? and is it worth updating the query or will the gain be minimal?
If the column has
a unique index: no, it's no faster
a non-unique index: maybe, because it will prevent sending any additional rows beyond the first matched, if any exist
no index: sometimes
- if 1 or more rows match the query, yes, because the full table scan will be halted after the first row is matched.
- if no rows match the query, no, because it will need to complete a full table scan
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