select if exists mysql

Similarly, using the goods table to practice subqueries, the table structure is as follows:All data (cat_id associated with category.cat_id):Category table:Mingoods (test when connecting queries)First, sub-query 1,where sub-query: The result of the

Installation RequirementsInstallation Environment: CentOS-6.3Installation Method: source code compilation installationSoftware Name: mysql-cluster-gpl-7.2.6-linux2.6-x86_64.tar.gzDownload Address: http://mysql.mirror.kangaroot.net/Downloads/Software

MySQL常用指令，java，php程序员，数据库工程师必备。程序员小冰常用资料整理MySQL common commands (for reference)The most common display commands are:1. Display the list of databases.show databases;2. Display the data table in the library:Use MySQL;Show tables;3, display the

Insert when MySQL record does not existIn MySQL, inserting (insert) A record is very simple, but some special applications, before inserting the record, need to check whether this record already exists, only if the record does not exist, the insert

How to configure MySQL database server on CentOS BitsCN.com accidentally found CentOS Professional Forum, remember: http://www.centospub.com As a result, the initial learning configuration This environment: CentOS system, Mysql-server (version

Insert when the MySQL record does not exist In MySQL, inserting a record is very simple, but in some special applications, before inserting a record, you need to check whether the record already exists. The insert operation is performed only when

When mysql processes a unique index, it updates the index. If it does not exist, it should be very common to insert the index. There are many similar articles on the Internet, today I will talk about the problems and methods that may occur when this

SQL query in the in, exists, not in, not exists usage and difference, sqlexists 1. in and exists In connects the External table to the internal table as a hash (Dictionary set), while exists loops the External table and queries the internal table

Usage and difference of in, exists, not in, and not exists in SQL queries 1. in and exists In connects the External table to the internal table as a hash (Dictionary set), while exists loops the External table and queries the internal table after

One query is as follows: 1 SELECTc.CustomerId, c.CompanyName   2 FROMCustomers c   3 WHEREEXISTS(   4