table_name where (set conditions here) limit 1 The "limit 1" will prevent the query from going beyond this threshold of results to delete. You may want to backup the table in question before you go forward with this. http://forums.mysql.com/read.php?21,135990,137776#msg-137776...
select * from t_table_1 where task_id in (select id from t_table_2 where uid = #{uid}) 1. 回到这条简单sql,包含子查询,按照我们的理解,mysql应该是先执行子查询:select id from t_table_2 where uid = #{uid},然后再执行外部查询:select * from t_table_1 where task_id in(),但这不一...
from table_name [where ...] [order by ...] limit s, n; 从s 开始,筛选 n 条结果,比第二种用法更明确 select ... from table_name [where ...] [order by ...] limit n offset s; 对未知表进行查询时,最好加一条 limit 1,避免因为表中数据过大,查询全表数据导致数据库卡死。
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Except one, Delete all duplicate records: 1 2 3 4 5 6 7 DELETE FROM tbl_RemoveDuplicate WHERE ID IN (SELECT ID FROM (SELECT id, ROW_NUMBER() OVER (partition BY Name ORDER BY ID) AS RowNumber FROM tbl_RemoveDuplicate) AS T WHERE T.RowNumber > 1); Check the result: 1 2 3 ...
Your outputisthe whole Persontableafter executing your sql. Usedeletestatement. 此题有两个解法: 我初步尝试用以下sql解决问题(要删除的记录Id肯定大于相同内容的Id): deletep1fromPerson p1, Person p2wherep2.id>p1.idandp2.Email=p1.Email;
(23000): Duplicate entry '1' for key 'PRIMARY' (gcdb@localhost) 11:20:28 [mytest]> replace into t4 values(1,10); -- 替换该主键对应的值 Query OK, 2 rows affected (0.00 sec) -- 两行记录受到影响 (gcdb@localhost) 11:20:54 [mytest]> select * from t4; +---+---+ | a | ...
Duplicate Weedout: Run the semijoinasifit was ajoinandremove duplicate recordsusinga temporary table.FirstMatch:Whenscanning the inner tablesforrow combinationsandthere are multiple instancesofa given valuegroup, choose one rather than returning them all. This"shortcuts"scanningandeliminates productionofunn...
分析select*fromt_table_1wheretask_idin(selectidfromt_table_2whereuid = #{uid}) 回到这条简单sql,包含子查询,按照我们的理解,mysql应该是先执行子查询:select id from t_table_2 where uid = #{uid},然后再执行外部查询:select * from t_table_1 where task_id in,但这不一定,例如我关了这个参数...
basically I want to remove thexxxx@nowhere.comrow where the cust_type is equal to 1...but only when there's a duplicate entry. Can anyone explain the syntax that I would have to use? I've tried looking into COUNT() and stuff like that but the combined syntax of COUNT() and DELETE...