我有一个varchar列的表,我想找到在这个列中有重复值的所有记录。我可以使用什么查询来查找重复项?
当前回答
进一步采取@maxyfc的答案,我需要找到所有返回的重复值的行,这样我就可以在MySQL Workbench中编辑它们:
SELECT * FROM table
WHERE field IN (
SELECT field FROM table GROUP BY field HAVING count(*) > 1
) ORDER BY field
其他回答
试着使用这个查询:
SELECT name, COUNT(*) value_count FROM company_master GROUP BY name HAVING value_count > 1;
SELECT
t.*,
(SELECT COUNT(*) FROM city AS tt WHERE tt.name=t.name) AS count
FROM `city` AS t
WHERE
(SELECT count(*) FROM city AS tt WHERE tt.name=t.name) > 1 ORDER BY count DESC
如果要删除具有多个字段的重复行,首先将它们取消为唯一不同的行指定的新唯一键,然后使用group by命令删除具有相同新唯一键的重复行:
Create TEMPORARY table tmp select concat(f1,f2) as cfs,t1.* from mytable as t1;
Create index x_tmp_cfs on tmp(cfs);
Create table unduptable select f1,f2,... from tmp group by cfs;
Select column_name, column_name1,column_name2, count(1) as temp from table_name group by column_name having temp > 1
我没有看到任何JOIN方法,它在复制方面有很多用途。
这种方法会给您带来实际的双倍结果。
SELECT t1.* FROM my_table as t1
LEFT JOIN my_table as t2
ON t1.name=t2.name and t1.id!=t2.id
WHERE t2.id IS NOT NULL
ORDER BY t1.name