select * 的好處和壞處

原創 纯洁的码农 2020-06-27 05:41

很多資料只說了這種寫法的壞處

1.取出全部的列會讓優化器無法完成索引覆蓋掃描這類油畫

2.會帶來額外的I/O 內存 CPU的消耗

好處

能提高相同代碼的複用性。

很簡單理解，有 a b c三類 ，如果我select * 那麼，我需要用到a b 的地方和需要用到 a c 的地方就可以用相同的代碼。

 

所以不要只看到他的壞處

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