前言原本這個主題應該與DQL 查詢資料（SELECT） 放在一起，後來想想這兩個子句還是特別獨立出來，因為相較於其他子句，其他子句是非常簡單易懂的， ... ... <看更多>

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To better understand having, you need to see it from a theoretical point of view. A group by is a query that takes a table and summarizes it ... ... <看更多>

No. They don't have to coexist, as proved by the fact that the following query in Oracle works: select * from dual having 1 = 1;. ... <看更多>