Our database has a table named City with data in the columns id, name, and country. idnamecountry 1 Madrid Spain 2 Barcelona Spain 3 Warsaw Poland 4 Cracow Poland Let’s get the names of the countries without duplicates. Solution: We’ll use the keyword DISTINCT. Here’s the query: SE...
SQL Server Show duplicates in multiple columns in UNION queryIf you are in an RDBMS platform that...
Or just use an inner join, but this will put the duplicates on the same row.You can do it ...
Removing duplicatesThe query was usingSELECT DISTINCTin such a way that MySQL could not optimize away the distinct operation at an early stage. Because of this, MySQL requires an extra stage to remove all duplicated rows before sending the result to the client. removing tmp tableThe thread is ...
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Removing duplicates 正在执行一个SELECT DISTINCT方式的查询,但是MySQL无法在前一个阶段优化掉那些重复的记录。因此,MySQL需要再次去掉重复的记录,然后再把结果发送给客户端。 Reopen table 获得了对一个表的锁,但是必须在表结构修改之后才能获得这个锁。已经释放锁,关闭数据表,正尝试重新打开数据表。
Removing duplicates正在执行一个Select DISTINCT方式的查询,但是MySQL无法在前一个阶段优化掉那些重复的记录。因此,MySQL需要再次去掉重复的记录,然后再把结果发送给客户端。 Reopen table获得了对一个表的锁,但是必须在表结构修改之后才能获得这个锁。已经释放锁,关闭数据表,正尝试重新打开数据表。
query end:处理查询之后,freeing items状态之前会发生这种状态。 Removing duplicates:该查询的使用SELECT DISTINCT方式使得MySQL不能在早期阶段优化不同的操作。因此,MySQL需要一个额外的阶段来删除所有重复的行,然后将结果发送给客户端。 removing tmp table:处理语句后,该线程正在删除一个内部临时表SELECT 。如果没有创...
Command: Query Time: 0 State: NULL Info: SHOW FULL PROCESSLIST 5 rows in set (0.00 sec) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. ...
§ Removing query cache entries after data in a table ischanged § Writing an event to the binary log § Freeing memory buffers, including for blobs · Killed Someone has sent aKILLstatement to the thread and it should abortnext time it checks the kill flag. The flag is checked in each ...