WHERE id IN（4）与WHERE id = 4有何不同？

Question

  

可能重复：
  Why would an IN condition be slower than “=” in sql?

执行之间是否有任何性能差异：

SELECT foo FROM bar WHERE id IN (4)

对战

SELECT foo FROM bar WHERE id = 4

Answer 1

我相信MySQL优化器会将id IN（4）转换为id = 4，因此没有性能差异