问题描述
我需要从mysql中的表中删除重复的记录.因此,我有一个表名"employee",字段为empid,empname,empssn
I need to delete duplicate record from table in mysql.So i have a table name "employee" fields are empid, empname, empssn
为了获取重复记录,我写了一个查询
for getting duplicate record i have written a query
SELECT COUNT(empssn), empssn
FROM employee
GROUP BY empssn
HAVING COUNT(empssn)>1
现在我要删除重复的记录.为此,我已经写了查询.
Now i want to delete duplicate records. for that i have written query is.
DELETE FROM employee
WHERE (empid, empssn) NOT IN (SELECT MIN(empid), empssn
FROM employee
GROUP BY empssn);
您可以假定表中的记录是
you can assume records in table are
EmpId EmpName EmpSSN
-------------------------------
1 Jack 555-55-5555
2 Joe 555-56-5555
3 Fred 555-57-5555
4 Mike 555-58-5555
5 Cathy 555-59-5555
6 Lisa 555-70-5555
7 Jack 555-55-5555
8 Mike 555-58-5555
9 Cathy 555-59-5555
10 Lisa 555-70-5555
11 Lisa 555-70-5555
但是我有一个mysql错误是
but i have a mysql error is
推荐答案
在这种情况下,将其包装到派生表中的技巧是否可行? (基于 http://www.xaprb.com/blog/2006/06/23/how-to-select-from-an-update-target-in-mysql/)
Does the trick of wrapping it into a derived table work for this case? (Based on http://www.xaprb.com/blog/2006/06/23/how-to-select-from-an-update-target-in-mysql/)
DELETE FROM employee WHERE (empid, empssn) NOT IN
(
SELECT empid, empssn FROM
(
SELECT MIN(empid) AS empid, empssn FROM employee GROUP BY empssn
) X
);
编辑是的,这似乎可行.
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