oracle表内查重

问：oracle查询表中是否有重复数据

1. 答：如果两列数据重复的话，可以通过count方法，找出计算条数大于1的，那么表示此条数据重复：
   sql: select district(*) from products having count(*)>1;
   备注：实际上两列重复的话，都是针对某个字段比较有意。
   sql:select name,count(*) from usertable group by name having count(*)>1;
   以上语句就是查询出名字重复的所有用户，并计算重复的次数。
2. 答：SELECT (SELECT COUNT(*) FROM 表名)-(SELECT COUNT(*) FROM (SELECT DISTINCT * FROM 表名)) 重复记录数 FROM DUAL;
3. 答：查单个字段：
   Sql代码
   SELECT TEST_NAME,COUNT(*) FROM T_TEST GROUP BY TEST_NAME HAVING COUNT(*) >1
   查组合字段：
   Sql代码
   SELECT TEST_NAME1,TEST_NAME2,COUNT(*) FROM T_TEST GROUP BY TEST_NAME1,TEST_NAME2 HAVING COUNT(*) > 1
4. 答：1、查找单个字段：
   select 字段名,count(*) from table group by 字段名 having count(*) > 1
   2、查找组合字段：
   SELECT TEST_NAME1,TEST_NAME2,COUNT(*) FROM table GROUP BY TEST_NAME1,TEST_NAME2 HAVING COUNT(*) > 1

问：如何查询oracle数据库表中的重复记录

1. 答：用group by ... having...
   比如查询，a,b,c,d四列组合是否有重复的
   select a,b,c,d,count(*)
   from tablename
   group by a,b,c,d
   having count(*) > 1

问：oracle/mysql表数据查重

1. 答：select user_name,count(*) as count from user_table group by user_name having count>1;

问：Oracle中对表中每个字段都做查重该如何写

1. 答：列出所有栏位:栏位1,栏位2,栏位3......
   select 栏位1,栏位2,栏位3,count(*)
   from user_table
   group by 栏位1,栏位2,栏位3
   having count(*)>1;
2. 答：使用distinct去重
   select distinct col1, col2, col3 from tab;

问：Oracle多字段表 统计完全重复记录

1. 答：SELECT COUNT(1) AS AMOUNT, A.A1, A.A2, FROM TABLE_A A GROUP BY A.A1, A.A2 having
   count(*) >= 2 ;

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