PHP PDO-使用提取时，是否需要LIMIT 1作为查询的一部分？

Question

So fetchAll will return an array, but fetch will return only one result:

fetch(PDO::FETCH_ASSOC);

My question is, if I have many rows on the table, would it be faster to also include LIMIT 1 in my query when using fetch , or is it totally unnecessary?

Answer 1

If you're only going to fetch one row, it's a good idea to use LIMIT 1 . This will reduce the load on the database, because it can stop processing the query as soon as it finds the first result. It also means less traffic over the network, because the server only needs to send back the first result; without this, the server will send lots of results that get buffered in the PDO library but never get used by the application.

Answer 2

It's not required, but it will generally result in a faster response. The database will not have to compute/collect the whole result set and can potentially do many optimisations if the limit is known.