delete duplicate rows in sql

it? "At that time, because it was a very simple question, it was directly completed using SQL statements. The interviewer said that there was a problem. I was wrong when I came back to study it. Now I will share the steps of the study. Study conditions: Window7 + no-install mysql 1. How to delete records with the same attributes except the primary key Main Idea: first, identify non-

Then I thought about a statement: The Code is as follows: Mysql> use mysqlDatabase changedMysql> select * from duplicate;+ ---- + ------- +| Id | name |+ ---- + ------- +| 1 | wang || 3 | wdang || 5 | wdand || 6 | wddda || 2 | wang || 4 | wdang |+ ---- + ------- +6 rows in set (0.00 sec)Mysql> delete

The SQL statement used to delete record duplication is one of our most common statements. The following describes how to delete record duplication in Oracle. It is helpful to you. 1. Search for redundant duplicate records in the Table. duplicate records are determined based

I read something about the Oracle database because of some database problems. For records in a table in an Oracle database, how can we delete repeated values. I will keep a record of my practices for future reference. The data I use is oracle. Suppose there is a table Create table test (name varchar2 (255), pass varchar2 (255 )); What should I do if the database has multiple rows of

Methods for deleting duplicate records (experiment description ):1. The table stu contains 16 data records, including select rowid, xh, xm, sex, birthday, classid, and degree from stu. Order by xh; 2. copy the data in the stu table into two copies for the experiment. After the experiment is copied, a total of 32 data entries are repeated, such. Insert into stu select * from stu; 3. for the same data, rowid is unique. Therefore, you can use rowid to

Delete from co_jobinformation Cwhere C.name in (select Cc.name from Co_jobinformation cc GROUP BY Cc.name have count (cc.name) > 1)and rowID not in (select min (rowid) from Co_jobinformation e Group by E.name have Count (e.name) >1)Previously in the Oracle database can delete duplicate data and can keep a unique data, but the same MySQL does not,MySQL has a featu

Tags: alt join plural comm LEFT outer join through the Ieft join color limitFirst we need to know what data we repeat,///Step one: Group the data tables, GROUP by.The second step: after the conduct through having to limit filtering, the number of bars greater than or equal to 2Step three: make multiple table deletions.Case:The first step is to group the data, and through having to restrict filtering, to obtain the presence of duplicate data Lao Wang,

SQL statements for querying and deleting duplicate records1, look for redundant records in the table, duplicate records are based on a single field (ID) to judgeSELECT * FROM table where ID in (select Id from table GROUP by ID have count (Id) > 1) 2, delete redundant records in the table,

Although I used to delete repeated records in the previous article, it was not bad, but I encountered a heavyweight large table, and I accidentally thought of a new method. Idea 1. keep records that are not repeated 2. Save a rowid in the record // 3. delete records whose rowid is not the rowid in step 2 of the original table, leaving one of the duplicate data

In thousands of records, there are some of the same records, how can you use SQL statements to delete duplicates?1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to judgeSELECT * from Peoplewhere Peopleid in (select Peopleid from People GROUP by Peopleid has count (Peopleid) > 1)2,

to do the same as the part of the individual name, and then update on it, but delete this I played an alias is not right, do not know whether I write wrong or not, I'll skip this method.I used the method is: first to find out the database of duplicate records in one of the data, this is not difficult, very simple, the SQL statement is as follows:Select * fromTe

Linux Delete duplicate lines of code In text processing, you often delete duplicate rows, and here are three ways First, with Sort+uniq, attention, simple uniq is not. ? 1 Sort-n Test.txt | Uniq Second, with the Sort+awk command, note that simpl

OracleSelect * fromGcfr_t_vch_delete EWHEREE.rowid(SELECT Max(X.rowid) fromGcfr_t_vch_delete XWHEREX.vchno=E.vchno andE.type=X.type andE.curragency=x.curragency);--orSelect * fromGcfr_t_vch_delete EWHEREE.rowid>(SELECT min(X.rowid) fromGcfr_t_vch_delete XWHEREX.vchno=E.vchno andE.type=X.type andE.curragency=X.curragency);The type of voucher, the number, the unit is the basis for judging the repetition. Delete Duplicates is to

#T a where exists (select 1 from #T where Num=a.num and Name=a.name and id>a.id)--keep only one recordGoALTER TABLE #T drop column id--Delete identity column--View ResultsSELECT * FROM #T/*Num Name----------- ----1 A2 B(2 rows affected)*/--use Method 3 after re-executing test dataMethod 3:Declare roy_cursor Cursor Local forSelect COUNT (1) -1,num,name from #T GROUP by Num,name have count (1) >1declare @con

Duplicate rows are often deleted during text processing. The following are three methods: First, use sort + uniq. Note that uniq alone cannot be used.Sort-N test.txt | uniq Second, use the sort + awk command. Note that awk alone does not work, for the same reason. Sort-N $ file | awk '{if ($0! = Line) print; line = $0 }' Third, use the sort + sed command, which also requires the sort command to b