Question

问题在于示例表结构：

mytable的

fielda, fieldb
val1    valx
val2    valy
val3    valz
val1    vala

我想从mytable中选择一个查询：

fielda, fieldb
val1    valx
val1    vala

基本上从表格中选择*，其中fielda是重复的。

然后使用不同的查询从mytable中选择

fielda, fieldb
val2    valy
val3    valz

fielda上的val1作为副本遇到，因此没有被选中，剩下的就是。

Answer 1

此查询对复制fieldA位于列表顶部的表进行排序。

SELECT  a.*
FROM    tableName a
        INNER JOIN
        (
            SELECT fieldA, COUNT(*) totalCount
            FROM tableName
            GROUP BY fieldA
        ) b ON a.fieldA = b.fieldA
ORDER BY b.totalCount DESC

SQLFiddle Demo

此查询仅选择重复记录。

SELECT  a.*
FROM    tableName a
        INNER JOIN
        (
            SELECT fieldA, COUNT(*) totalCount
            FROM tableName
            GROUP BY fieldA
        ) b ON a.fieldA = b.fieldA
WHERE b.totalCount > 1
ORDER BY b.totalCount DESC

SQLFiddle Demo

和这个，选择不在第二个查询上的记录（上面）

SELECT  a.*
FROM    tableName a
        INNER JOIN
        (
            SELECT fieldA, COUNT(*) totalCount
            FROM tableName
            GROUP BY fieldA
        ) b ON a.fieldA = b.fieldA
WHERE b.totalCount = 1
ORDER BY b.totalCount DESC

SQLFiddle Demo

Answer 2

select fielda, fieldb from mytable group by fielda having count(*) >1

select fielda, fieldb from mytable group by fielda having count(*) =1

Answer 3

第一个：

SELECT * FROM tbl GROUP BY fielda HAVING COUNT（*）＆gt; 1

第二个：

SELECT DISTINCT（fielda）FROM tbl

select * duplicatelicates，然后选择* non-duplicates - mysql

3 个答案: