MySQL

This article uses an example to illustrate how to delete duplicate database records in mysql. If you need it, refer to the example. Demo data Table Structure:   The Code is as follows: Copy code Mysql> desc demo;+ ------- + --

In MySql4.0.12, after using the "create table bak_name as select * from original_name" statement The generated bak table does not have a primary key and an index. When using it, you must note that you can first create one and the table structure to

The mysql tutorial does not use the rand () function to randomly read database tutorial records.As well as google's related files, we found that order by rand () is almost the same, but there are actually very serious performance problems.If your

SQL isnull (oracle, mysql tutorial, mssql) IsnullReplace null with the specified replacement value. SyntaxIsnull (check_expression, replacement_value) ParametersCheck_expression Whether the expression is null is checked. Check_expression can be of

This tutorial describes how to query and delete the mysql view. You can use the show view name to query the view and delete the mysql view with the drop permission. However, you must have the drop permission to delete the view. Next let's take a

Mysql common password recovery methods/* 1. if you forget the MySQL root Password, use the following methods to reset the password: 1. KILL the MySQL process in the system; Mysql tutorials/*I. One of the methods to restore the MySQL passwordIf you

1. test PROCEDURE.DELIMITER $Drop procedure't _ girl '. 'SP _ split_table' $Create procedure't _ girl '. 'SP _ split_table '()BEGINDeclare done int default 0;Declare v_user_name varchar (20) default '';Declare v_table_name varchar (64) default '';--

Mysql SQL stored procedure condition definition and processing. The condition definition and processing of the stored procedure can define the problems encountered during the processing for corresponding processing. Definition and processing of

Mysql command line import. SQL data to the database 1. First open the mysql tutorial in the command line ConsolePerhaps the command is as follows:Mysql-u root-p database_nameThen you may be prompted to enter the corresponding Password2. The

MySQL uses multiple statements in the Exception Handling Section of the stored procedure-- Create a test table without any dataDrop table if exists t;Create table t (id int );-- Create a stored procedureDrop procedure if exists test;Delimiter

The query cache mechanism of Mysql is QueryCache, which is based on SQL statements. If an SQL query starts with select, the MySQL server will try to use QC for it. Each Cache is saved using SQL text as the key. Before QueryCache is applied, SQL text

Select * from table1 where name = 'hangsan' and tID> 10000And execution:Select * from table1 where tID> 10000 and name = 'hangsan'Some people do not know whether the execution efficiency of the preceding two statements is the same, because the two

SQL PRIMARY KEY instance tutorial Database primary key constraintsThe primary key constraint uniquely identifies each record in a database table.The primary key must contain unique values.The primary key column cannot contain null values.Each table

How does MySQL simplify external Union? In many cases, the expression of a table in the FROM clause can be simplified. During the analysis phase, queries with right Outer Join Operations are converted to equivalent queries that only contain left

Change the mysql password, mysql change the root password, how to change the mysql password, mysql change the User Password First, we need to declare that, in most cases, modifying MySQL requires the root permission in mysql. Therefore, users cannot

I am using a linux system, but the mysql database on the website cannot be connected. I want to restart it. After the restart, mysql prompts mysql daemon failed to start, I will search for some solutions below. If you need them, please refer to them.

After the mysql master-slave settings, if the operation is improper, the data on server B of server A will be automatically deleted simultaneously. If the deletion is wrong, it means that you have not backed up the database, the following section

The most garbled mysql Chinese is the database encoding problem. If our database encoding is the latin1 character set, but we save the gbk directly, Chinese garbled characters may occur, below I have summarized some solutions. View my instance first

Many of you know that you can only use group by to count the number of groups but not the amount of data. Some may use count to count the number of groups. In fact, you can configure group by SQL _CALC_FOUND_ROWS for the instance. Mysql can obtain

We may use update and replace into for batch update in mysql. The following section will detail mysql batch update and performance. Batch update The mysql update statement is simple. to update a field of a piece of data, write as follows: