how to eliminate duplicate records in sql

Parsing mysql: unique query for single table distinct and multi-table groupby to remove duplicate records bitsCN.com single table: distinct Unique query for multiple tables: group When distinct queries multiple tables, left join is still valid and full join is invalid, When using mysql, you sometimes need to query records with unique fields. Although mysql provid

Unique query for a single table: distinct Unique query for multiple tables: group When distinct queries multiple tables, left join is still valid and full join is invalid, When using mysql, you sometimes need to query records with unique fields. Although mysql provides the keyword distinct to filter out redundant duplicate records, only one record is retained, bu

use a statement query to get the name does not duplicate all the data, it must use distinct to remove unnecessary duplicate records. select DISTINCT name from table the results obtained are:Name A C It seems to be working, but what I want to get is the ID value? Change the query statement: SELECT DISTINCT name, ID from table The result will be:ID Name 1 A 2 b

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

A previous deletion of duplicate records although it's not bad, but when I met the heavy scale, I was too powerless to think of a new method. Thinking 1, keep the record of not duplicate 2. Save a ROWID in a duplicate record 3, delete the original table rowid is not rowid in step 2

1. Duplicate records can be identified by a single field: ID 1 and the name of ID 6SELECT * FROM student where name in (select name from student Group by name H aving COUNT(name) >1)In operator: Allows multiple values to be specified in the WHERE clause; GROUP by: Groups The result set by name; The Having:where keyword cannot be used with the aggregate function;Delete from student where name in (select name

Unique query for a single table: distinctUnique query for multiple tables: groupWhen distinct queries multiple tables, left join is still valid and full join is invalid,When using mysql, you sometimes need to query records with unique fields. Although mysql provides the keyword distinct to filter out redundant duplicate records, only one record is retained, but i

; CREATE TABLE TMP2 Select tablename.* from tablename,tmp where tablename.autoid = tmp.autoid; drop TABLE TableName; Rename table Tmp2 to TableName; SQL Server Select Identity (int,1,1) as Autoid, * into #Tmp from TableName; Select min (autoid) as autoid into #Tmp2 from #Tmp Group by name,address; drop TABLE TableName; SELECT * INTO TableName from #Tmp where autoid in (select Autoid from #Tmp2); drop table #Tmp; drop table #Tmp2; Oracle DE

filter out excess duplicates, but it often only uses it to return the number of records that are not duplicates, rather than using it to return all values that are not logged. The reason for this is that distinct can only return its target field, and cannot return other fields, which bothers me for a long time. Let's take a look at the following examples: The code is as follows Copy Code TableID Name1 A2 b3 C4 C5 b

single-table only query by: DISTINCTUnique query for multiple tables: Group byDistinct when querying multiple tables, the LEFT join is valid and the full connection is invalid.When using MySQL, it is sometimes necessary to query for a record that does not duplicate a field, although MySQL provides the DISTINCT keyword to filter out redundant duplicate records to

Tags: mysql distinctAlthough distinct is a syntax for SQL and does not belong to MySQL, here is an example of MySQL.After so many years of distinct, incredibly has been wrong. Always thought that distinct is the removal of duplicate fields, originally it is to remove duplicate records.A repeating record is a record in which all fields are the same after distinct.

Repeat | duplicate record Usually choose duplicate records, all need to use distinct, but there is a bad place, that is, can not select multiple fields, Internet search for a long, in the dynamic network found a paste to solve this problem, the use of the following statement: Sql= "Select a,b from tab where ID to (sel

Label:MongoDB version number is, MongoDB shell version:2.4.4The operating environment, Shell window, is as follows: [mongo_user@mongodb_dbs ~]# mongo --port 30100 2.4.4 127.0.0.1:30000/test mongos> usepos pos 1, the first statistical grouping records, the Paymentorder field to group statistics, to find out all the statistical results, the group statistics of >1// 这里分组统计出来取分组字段paymentOrder的值_id、最大的objectid值max_id、分组统计数count vargroup=([ {$grou

Method and code for deleting duplicate records in MYSQL (2) bitsCN.com 4 rows in set (0.00 sec) Mysql> create temporary table tmp_wrap select * from users_groups group by uid having count (1)> 1 union allSelect * from users_groups group by uid having count (1) = 1;Query OK, 7 rows affected (0.11 sec)Records: 7 Duplicates: 0 Warnings: 0 Mysql> truncate table users

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 se

complete the operation. You can only sort the operation. When using mysql, you sometimes need to query records with unique fields. Although mysql provides the keyword distinct to filter out redundant duplicate records, only one record is retained, but it is often used to return the number of records that do not repeat

Sometimes there are some wrong databases, and some duplicate records are generated in the table. It is troublesome to delete Redundant records. Today, we can see a clever solution, taking advantage of the MySQL extension feature, we simply completed this task. Why make this such a challenge? Assuming your example:Create Table bad_table2 (Id int not

with duplicate data. This process seems complex, in fact, only the implementation of group by in the T-SQL... Having... . var ds=db.paymentinfo.aggregate(group, match); PS: the match is invalid. A lot of data with the count value of 1 is displayed, that is, {"match": {"count": {"gt": 2 }}; failed, why? 4. Back up the data before deletion. Backup /usr/local/mongodb/mongodb-linux-x86_64-2.4.4/bin/mongoexpor

(NOLOCK) group by TID,SN have COUNT (0) >1Delete Dorecordproperty from#Tmp p where P.tid=dorecordproperty.tid and p.sn=dorecordproperty.sn and Dorecordproperty.idSelect COUNT (0) as num from #Tmp--query data for temporary tablesTRUNCATE TABLE #Tmp-Clears all data and constraints for the staging tabledrop table #TmpSET NOCOUNT OFF Sure enough, in 40 seconds, the execution was successful. The above is on the server: CPU 2u e5-2620; memory 96G HDD is 1T enterprise level 7200 RPM; Data is operati

ORACLE: Delete duplicate records in the database Select corpname, count (*) from tbcorp group by corpname having count (*)> 1 Delete from tbcorp A where a. rowid! = (Select Min (B. rowid) from tbcorp B where a. corpname = B. corpname) The project applied to the Local Adjustment Center has the following SQL statement:Select blockid, nodeno, count (*) from geop