Question

我的表包含以下条目

Id  |   Accno  |    Name   |    Hash
----+----------+-----------+---------
 1  |    11    |     ABC   |    01110
 2  |    11    |     ABC   |        
 3  |    22    |     PQT   |        
 4  |    33    |     XYZ   |    03330
 5  |    44    |     LMN   |    04440
 6  |    33    |     XYZ   |

我需要SQL查询来从表中删除重复条目，并在表中存在哈希值的至少单个条目。对于那些不重复的条目，也应保留在表格中。

Answer 1

我认为你们经常使事情过于复杂化。这应该只是花花公子：

DELETE FROM 
    YourTable
WHERE Hash IS NULL
AND Accno IN 
    (
    SELECT Accno
    FROM YourTable
    GROUP BY Accno
    HAVING COUNT(Name) > 1
    )
;

Answer 2

最简单的方法可能是创建一个新表并复制非重复的条目。

create table table_name2 as select distinct * from table_name1;
drop table table_name1;
rename table_name2 to table_name1;

像这样。

Answer 3

Create table temp2 as SELECT *
FROM temp where id in (select id from temp group by accno having count(accno)>=1 and hash<>'');    
drop table old_table;
rename table temp2 to old_table;

检查SQL Fiddle

用于从表中删除多个重复条目的SQL查询

3 个答案: