Mysql Duplicate Row

Method 1 delete yourtable where [id] not in (select max ([id]) from yourtable group by (name + value) b on a.id = b.id where b.id ...

SQL used to manipulate the database is generally divided into two kinds, one is the query, which is what we call the SELECT statement, the other is to update the statement, also known as data manipulation statements. The implication is to modify the data. There are 3 statements in the standard SQL, which are INSERT, UPDATE, and DELETE. There is another REPLACE statement in MySQL, so this article uses MySQL as a background to discuss how to make updates in SQL. First, INSERT and REPLACE I ...

When querying data, we often need to specify a few rows of data to be returned. As now there is a B/s architecture application, each page may display only 30 records. In order to improve the efficiency of the display, the database is generally required to return only 30 records at a time. When the user presses the next page, return 30 records from the database, and so on. This can shorten the time that the data is displayed. This is very effective when the base table for the query is larger. You can use the Limit keyword to implement this requirement at this time. The limit clause can be used to force a SELECT query statement to return ...

The complete collection of SQL statement operations deserves to be permanently stored the following statements are part of the MSSQL statement and are not available in Access. SQL classification: ddl-data Definition language (create,alter,drop,declare) dml-Data Manipulation Language (Select,delete,update,insert) dcl-Data Control Language (Grant,revoke, Commit,rollback first, briefly introduce the basic statement: 1, Description: Create number ...

Intermediary transaction SEO diagnosis Taobao guest Cloud host Technology Hall log is a very broad concept in computer systems, and any program may output logs: Operating system kernel, various application servers, and so on. 　　The content, size and use of the log are different, it is difficult to generalize. The logs in the log processing method discussed in this article refer only to Web logs. There is no precise definition, which may include, but is not limited to, user access logs generated by various front-end Web servers--apache, LIGHTTPD, Tomcat, and ...