在mysql中有没有与oracle的rowid等价物?
delete from my_table where rowid not in (select max(rowid) from my_table group by field1,field2)
我想创建一个与此查询等效的mysql!
我想要做的是: my_table没有主键。我正在尝试删除重复的值并添加一个主键(由field1、field2组成)..!!
发布于 2011-11-12 04:46:37
也许,我误解了这个问题,但您的查询(即使是在Oracle中)也没有达到您期望的目标:
delete from my_table where rowid not in (select max(rowid) from
my_table group by field1,field2)
MySQL的等价物是
SELECT @rowid:=max(rowid) from my_table;
DELETE FROM my_table where rowid != @rowid;
这将清除除最后一行之外的所有行。
要对数据执行一次性清理(删除重复记录),您可以执行以下操作:
CREATE TABLE my_table2 SELECT distinct f1, f2, f3, etc from my_table;
DROP TABLE my_table;
ALTER TABLE my_table2 RENAME my_table;
然后添加ALTER TABLE所需的任何列和键。上面的代码可能需要删除你可能拥有的任何外键。
发布于 2018-06-11 11:47:30
mysql> set @row_num = 0;
首先设置rowId或行数使用它,如下所示:
mysql> SELECT @row_num := @row_num + 1 as row_number,id,name,salary FROM employee
ORDER BY salary;
发布于 2010-12-30 04:26:43
您可以使用另一个派生表来避免使用临时表:
DELETE FROM my_table USING my_table JOIN (
SELECT @rowid:=IF(@f1=field1 AND @f2=field2, @rowid+1, 0) as rowid,
@f1:=field1 as field1,
@f2:=field2 as field2,
some_row_uid
FROM testruns t, (SELECT @rowid:=NULL, @f1:=NULL, @f2:=NULL) as init
ORDER BY field1, field2 DESC) as duplicates
ON my_table.some_row_uid = duplicates.some_row_uid AND duplicates.rowid > 0
https://stackoverflow.com/questions/2728413
复制相似问题