如果按列的計數大於1，如何刪除特定列中值最小的行

Question

我有一張如下表所示的名稱推薦

我想刪除所有cnt具有最小值並且存在多個ID_recipient記錄的行。

如果只有一條ID_recipient記錄，則無論cnt值是多少，它都不應該被刪除。

藍色突出顯示的是必須保留的記錄。

我試過了：

DELETE from table where( 
    SELECT DISTINCT(A.ID_recipient), DISTINCT(A.cnt) FROM (
          SELECT  MIN(cnt) as cnt FROM recomendation_table_ID_recipient GROUP BY ID_recipient HAVING COUNT(*) > 1 ) as A);

這是行不通的。

Answer 1

如果要使用二維，則必須使用 IN 子句。

你的子查詢沒有多大意義，所以你應該先測試一下，或者用想要的例子發布數據

DELETE from recomendation_table_ID_recipient where (ID_recipient,cnt) IN ( 
    SELECT DISTINCT A.ID_recipient, A.cnt FROM (
          SELECT ID_recipient, MIN(cnt) as cnt FROM recomendation_table_ID_recipient GROUP BY ID_recipient HAVING COUNT(*) > 1 ) as A);

Answer 2

delete t1 from recomendation_table_ID_recipient t1 join (
    select ID_recipient, min(cnt) as cnt from recomendation_table_ID_recipient
    group by ID_recipient
    having count(*) > 1
) t2 on t1.ID_recipient = t2.ID_recipient and t1.cnt = t2.cnt;

見分貝小提琴