MySQL

Usage Notes: Ifnull (EXPR1,EXPR2)If EXPR1 is not Null,ifnull () returns EXPR1, it returns EXPR2.Ifnull () returns a numeric or string value, depending on the context in which it is used.Let us first cite some examples:Mysql> SELECT ifnull (1,0); +---

1 worm Replication Worm replication: Data is fetched from existing data and then added to the data, which multiplies. Table creation Advanced Action: Create a new table from existing (duplicate table structure) Create

First, Introduction　　is a classic RDBMSthat currently belongs to Oracle Advanced MySQL contains the content:　　　MySQL kernel SQL optimization engineer MySQL server optimization various parameters constant set query statement optimizationMaster-slave

--more needs to be understoodhttp://hedengcheng.com/?p=577--Ho Dengcheng on the Where extractionHttp://www.cnblogs.com/metoy/p/5545580.html--About the deadlock analysis 1Http://www.jb51.net/article/32651.htm--About the deadlock analysis

1. Create an Account1) Read-only accountGRANT USAGE on *. testgao_r ' @ ' 192.168.1.1 ' identified by ' password ' with Max_queries_per_hour 14400000 Max_updates_pe R_hour 7200000 max_connections_per_hour 14400000 max_user_connections 2000;GRANT

Uninstall method One:--delete MySQL data filessudo RM/var/lib/mysql/-R--delete the MySQL configuration filesudo RM/etc/mysql/-R--Automatically uninstall MySQL (both server and client)sudoApt-get Autoremove mysql*--Purgesudoapt-Get Remove AppArmor--

1. Integral type MySQL data type Meaning (Signed) tinyint (m) 1 byte range ( -128~127) smallint (m) 2 byte range ( -32768~32767) Mediumint (M) 3 byte range ( -8388608~83

-(SELECTNULL, product_id, Product_Name,Count(Op. Number) as Number,--sum (total_amount + POINT_TOTAL_AMOUNT/10) asTotal_amount,--sum (point_total_amount) asPoint_total_amount-- from----(SELECT * FROM orders where (status = ' Completed ' and (Refund_

Recently, mainly in the software development of the document, how to write the requirements of the document, how to build UML and CDMThen I thought of MySQL, decided to start with MySQL and then go back to OracleMaster-slave replication principle.

mysql5.1.6 adds an event scheduler (Scheduler) that can do timed tasks (time-lapse records, timed data statistics) instead of the previous system's scheduled tasks. The MySQL event Scheduler can perform a task exactly one second.The difference

Restoration of master-slave replication failure in mysqlPreface:Because the Host Name of the linux server is modified, mysql master-slave replication becomes invalid. Now you need to restore master-slave replication. This is a bit different from

Mysql-function case when counts multiple fields, mysql-case The case when statement is used to calculate the condition list and return one of multiple possible result expressions.CASE has two formats:1. Simple case functions: case input_expression

Basic MySQL operations -- Connect to the mysql database (the premise is to configure the environment variable of the MySQL database and add path)Mysql-uroot-p -- Set the input and output encoding of the text: cmd uses gbk, otherwise garbled

MySQL (6), mysql1 foreign key Foreign key: foreign key, the external key (the key is not in the table itself). If a field (non-primary key) in a table points to the primary key of another table, this field is called a foreign key.  1.1 add

MySQL grants PROCESS permissions to common users.     How to authorize normal users to viewAll user threads/Connection permission. Of course, by default, show processlist can view the thread/connection of the current user.     Mysql> grant

[MySQL] Quick Solution for "is marked as crashed and shoshould be retried red" faults, crashedretries red The specific error is as follows:Table '. \ mysql \ proc' is marked as crashed and shoshould be retried red My solution:Find the

About the connection problems and troubleshooting methods encountered in daily use of Azure MySQL, azuremysql Due to firewall problems, TCP keep alive problems, and MySQL parameter problems, these three problems are common in use. So today I will

Database optimization methods and database Optimization Methods1. select the most suitable field attribute MySQL can support access to large data volumes, but generally, the smaller the table in the database, the faster the query will be executed on

Four Methods for DB master-slave consistency Architecture Optimization and four methods for db master-slave consistencyI. Origin of demand Most Internet businesses use "read-write-less" scenarios. At the database level, read performance often

MySQL (4), mysql1. worm Replication Worm replication: obtains data from existing data, and then adds new data. The data increases exponentially.   Advanced Table creation operations: Create a new table from the existing table (copy the