delete duplicate rows in sql

When text processing, you often want to delete duplicate rows, here are three ways First, with Sort+uniq, note, simple uniq is not. Sort-n Test.txt | Uniq Second, with the Sort+awk command, note that simply awk also does not, the same reason. [Email protected] ~]$ uniq--help usage: uniq [options] ... [File] Filters adjacent matching

Take PostgreSQL 9.2 official document as an example: Create table weather (City varchar (80 ),Temp_lo int, -- low temperatureTemp_hi int, -- high temperaturePrcp real, -- precipitationDate); Insert into weather VALUES('San Francisco ', 46, 50, 0.25, '2017-11-27 '),('San Francisco ', 43, 57, 0, '2017-11-29 '),('Hayward ', 37, 54, NULL, '2017-11-29 '),('Hayward ', 37, 54, NULL, '2017-11-29'); --- duplicated row Here are the three methods: Method 1: Replacement -- Remove

This article describes how to delete duplicate rows in a text file in php. it involves some skills related to php operations on text files and is of great practical value, for more information about how to delete duplicate rows in

Php deletes duplicate rows in a text file, This example describes how to delete duplicate rows in a text file in php. Share it with you for your reference. The specific analysis is as follows: This php function is used to delete

how PHP deletes duplicate rows in a text file The example in this article describes how PHP deletes duplicate rows in a text file. Share to everyone for your reference. The specific analysis is as follows: This PHP function is used to delete

, and row of each record in Oracle. In a duplicate record, the content of all columns may be the same, but the rowid may not be the same. Therefore, you only need to determine the rows with the largest or least rowid in the record, delete all others. SQL> delete from employe

described in two parts: user_id and ID. I. Check user_id first 1. The effects of Count (ID) and count (user_id) after group by user_id are different. The following statement indicates that three rows of user_id are null, and count (null) seems invalid. 2. Make the userid in (null, 1257646) and user_id in (1257646) statements consistent, and the previous null will be ignored. In fact, all results are user_id in (1257646 ). Can it be u

The first thing to see is that we are using Excel software, is excel2003 or 2007 or 2010. Usually 2007 and 2010 are similar, and all we need to know about excel2003 and 2007 is the way Excel2003 method of Operation one: Step one: If the two rows of data are the same, as shown in the figure: Step Two: Select all the records in the table first, select the "Data"-"filter" above the menu bar to select the Advanced Filter option in the Drop-down list,

Employe E2 where e1.emp_id=e2.emp_id and E1.emp_name=e2.emp_name and E1.salary=e2.salary); emp_id Emp_name SALARY ---------- ---------------------------------------- ---------- 1 Sunshine 10000 3 xyz 30000 2 Semon 20000 2. Several methods of deletion: (1) By establishing a temporary table to achieve Sql>create table Temp_emp as (SELECT DISTINCT * from employee) Sql> TRUNCATE TABLE employee; (Empty the Empl

emp_name salary ------------------------------------------------------------ 1 sunshine 10000 2 semon 20000 SQL> select * from employee E1 Where rowid in (select max (rowid) from employe E2 Where e1.emp _ id = e2.emp _ id and E1.emp _ name = e2.emp _ name and e1.salary = e2.salary ); Emp_id emp_name salary ------------------------------------------------------------ 1 sunshine 10000 3. XYZ 30000 2 semon 20000 2.