常用SQL

1.查找表中单个字段的值有哪些相同的记录:

假设表名是table，列名是column，则查询语句为：

SELECT * FROM table WHERE column IN (SELECT column FROM table GROUP BY column HAVING COUNT(column)>1)

2.查找表中多个字段的值有哪些相同的记录:

假设表名是table，列名是column1,列名column2,则查询语句为：

SELECT A.* FROM table A RIGHT JOIN (SELECT column1,column2 FROM table group by column1,column2 HAVING COUNT(*)>1 )  B ON A.column1 = B.cloumn1 AND A.column2 = B.column2