查询后追加的LIMIT 1是否有任何性能提升？@H_301_2@

…如果只有一个匹配的可能条目(主键的WHERE子句)？@H_301_2@

@H_301_2@

SELECT `x`
FROM `unicorns`
WHERE `id` = 123
LIMIT 1

…相同,但现在它是DELETE：@H_301_2@

@H_301_2@

DELETE FROM `unicorns`
WHERE `id` = 123
LIMIT 1

……和更新：@H_301_2@

@H_301_2@

UPDATE `unicorns`
SET `rainbows` = `rainbows` + 1
WHERE `id` = 123
LIMIT 1

附：列ID是主键,因此它是唯一的.@H_301_2@

谢谢你的建议！@H_301_2@