duplicate annihilator

In the system will inevitably exist duplicate files, these duplicate files will occupy our large amount of system space, thus affecting the speed of our operation. Therefore, we need to clean up these duplicate files, so let's take a look at the master's clean-up coup. Use ACDSee to clean up system duplicate files No

First Solution: If you specify the on DUPLICATE KEY Update command statement, the duplicate contents of the database record will not be inserted under the unique index or the primary index, but the old records in the database are also updated. For example, a field A is declared as a unique index and contains only records with a value of 1, and the following two statements achieve the same effect:

Tags: src not tin cursor have compare people fetch lookup1 , duplicate records in the lookup table are judged by a single field (Peopleid).SELECT * from peoplewhere Peopleid in (select Peopleid from People GROUP by Peopleid have count (Peopleid) > 1) Example Two: Select * from TestTable where numeber in (theselect number from the People Group by number has a count (number) > 1) you can find the same number of records in the TestTable table.2, dele

Thanks to Sun Yunan's summary, address http://www.cnblogs.com/sunxiaonan/archive/2009/11/24/1609439.htmlFor example:ID Name Value1 a pp2 a PP3 B III4 B pp5 B pp6 C pp7 C pp8 C IIIID is primary keyAsk for such a resultID Name Value1 a pp3 B III4 B pp6 C pp8 C IIIMethod 1Delete yourtablewhere [id] not in (Select MAX ([id]) from yourtableGroup BY (name + value))Method 2Delete aFrom Table a LEFT join (Select Id=min (ID) from table GROUP by Name,value) B on A.id=b.idwhere b.id is nullSQL statement fo

Label:SQL statement for querying and deleting duplicate records1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to determineSELECT * from Peoplewhere Peopleid in (select Peopleid from People GROUP by Peopleid have count (Peopleid) > 1)2, delete redundant records in the table, duplicate records are based on a sin

SQL Single Table/multiple table query removal duplicate record single table distinct multiple table group byGroup byMust be placed inOrder byand limit before the error will be************************************************************************************1, duplicate records in the lookup table are judged by a single field (Peopleid) .Select * frompeoplewherePeopleidinch(SelectPeopleid fromPeopleGrou

Tags: Ignore duplicate data 0.00 Having uniqueness key distinct inserting Data tabThere may be duplicate records in some MySQL data tables, and in some cases we allow duplicate data, but sometimes we also need to delete the duplicated data. In this blog post we will show you how to prevent data tables from repeating data and how to delete

Brief Introduction For us, disk loading is one of the thorny issues. No matter how cautious we may be, we can always copy the same files to many different places or, without knowing it, repeatedly download the same file. As a result, sooner or later you will see "Disk full" error prompts, and if we do need some disk space to store important data at this point, the above scenario is the worst. If you are sure that there are duplicate files in your sys

MySQL "on DUPLICATE KEY UPDATE" syntaxif on DUPLICATE KEY UPDATE is specified at the end of the INSERT statement and the row is inserted causing duplicate values in a unique index or primary key, the update is performed on the row where the duplicate value occurs ; Insert a new row if the problem does not cause a uniqu