MySQL

Suppose that a website contains the table and the table tables Customers Orders . Write a SQL query to find all customers The WHO never order anything.Table: Customers .+----+-------+| Id | Name |+----+-------+| 1 | Joe | | 2 | Henry | | 3 |

Performance optimization is divided into four chunks:Table StructureOptimization (with index)SQLOptimization of the statement bottomParametersOptimizationHardwareConfiguration optimization   table structure     Selecting the appropriate data type

I believe many friends in the process of using MySQL will encounter this problem, the installation process error, or want to change version, or do not want to use, this time we need to completely uninstall MySQL? Next, let's talk about my experience.

1. Find the foreign KEY constraint name for the databaseSELECT A.constraint_name,b.table_name from INFORMATION_SCHEMA. Referential_constraints A,information_schema. TABLES b WHERE a.table_name=b.table_name and B.table_schema = ' test ';2. Delete a

Installation There is nothing to say, according to WDCP official to do it, here if it is the CentOS system recommended to use the RPM installation of accessories as follows (this contains three files later in this

Example Description:Main Library ip:0.0.0.43From library ip:0.0.0.194First, Configuration Main Library (0.0.0.43 )1, edit the main library configuration file /etc/my.cnf, note the location, add under [mysqld] , do not add to [Mysqld_safe]

Reference from http://blog.csdn.net/allens_zhou/article/details/8575400Centos7 64bitYum Install UnixODBC unixodbc-devel MYSQL-CONNECTOR-ODBCVim/etc/odbcinst.ini# Example Driver definitions# driver from the PostgreSQL-ODBC package# Setup from the

Mysqldump:got error:145:table ' wp_options ' is marked as crashed and should being repaired when using LOCK TABLESThe error is as shown above.Today in to their own WP site, when the export data found not to come out, reported as the error, in the

Due to the need to configure MySQL master-slave synchronization configuration, the configuration process is now recorded, in case of future contingencies1.1. Synchronous IntroductionMySQL's master-slave synchronization is an asynchronous replication

This article is for the use of the MySQL database under Ubuntu system, the MySQL version is: Ver 14.14 distrib 5.5.43(MySQL version can be entered in the command line MySQL--version display)I. MySQL INTRODUCTIONMySQL is an open-source relational

For example, a table user (Id,name) has a search on the ID primary key.Test:1. Build a table usersCreate table:create Table ' users ' (' id ' int (one) is not NULL,' Name ' varchar (255) DEFAULT NULL,PRIMARY KEY (' id ')) Engine=innodb DEFAULT

1. Copy Date folder Backup ============================ hypothetical environment: MySQL Installation Location: C:\MySQL Forum database name: BBS database backup destination: C:\db_bak\ ====== ====================== New Db_bak.bat, write the

Today work found Zabbix alarm, open the alarm page looked down, said the server/partition is less than 20%.SSH to server, view results found to be MySQL Bin-log file resulting in usage less than

Definition and usageThe Date_format () function is used to display date/time data in different formats.GrammarDate_format (Date,format) The date parameter is a valid day. format Specifies the date/time in which the output is formatted.The formats

1.unix_timestampConverts a time into a timestamp. (date type data converted to timestamp form integer)Time stamp of the current time without passing the time parameterMysql> select Unix_timestamp ();+------------------+| Unix_timestamp () |+---------

Version information for Linux,mysql and R: Linux naci 3.19.0-16-generic #16-ubuntu SMP Server VERSION:5.6.24-0UBUNTU2 (Ubuntu) R version 3.1.2 (2014-10-31)--"Pumpkin Helmet" MySQL Linux installation, refer to the previous article about

MySQL data is recently needed to be integrated into HBase, using MapReduce to create a job to import MySQL data.In the process of accessing the data, we found the tools that open source tools Sqoop (relational database and hdfs,hbase,hive, etc.)

Use of MySQL common indexes, unique indexes, primary indexes, foreign key indexes, composite indexes, and full-text indexes1. Common Index The only task of a common INDEX (INDEX defined by the KEY or INDEX keyword) is to speed up data access.

MySQL obtains the first N records of all categories. For example, if you have an Article table Article (Id, Category, InsertDate), you need to use SQL to find a set of the First N data records of the latest time in each type. It has a good piece of

Install MySQL5.6 and modify the root password.1. After MySQL5.6 is installed, MySQL cannot be enabled properly. 1. After decompression, go to my computer> Properties> advanced> environment variables.Select PATH and add the PATH of the mysql bin