MySQL

> Little is a little lazy. Plus winter cold more don't want to move. But now the problem is getting more and more, I think the summary is still essential ah and the summary will be a lot more enlightened! so first from the about linux

Storage Engine Supported locks MyISAM Table-Level Locks MEMORY Table-Level Locks InnoDB Row-level Locks BDB Page lock Table-level Lock: Low overhead,

------------------------------------------------------------------------------------------------[Create stored procedure, use variable, random number]DELIMITER $$DROP PROCEDURE IF EXISTS ' Week_luck_call ' $$CREATE PROCEDURE Week_luck_call

Hive Chinese garbled problemAs we all know, we are using the MySQL storage hive metadata, you can execute with Chinese comments in the table file, to solve the problem of Chinese garbled:To set the metabase to Latin1 and set the encoding of the data

Mysql-u root-pMysql>use MySQL;Mysql>select ' host ' from user where user= ' root ';Mysql>update User Set host = '% ' where user = ' root ';(error.Mysql>flush privileges;Mysql>select ' host ' from user where user= ' root ';The first sentence is to

These two days have a very strong feeling is oneself in some special situation or hold, the brain is easy to empty or say suddenly do not know how to analyze the problem, for example, ask "hash and btree Index difference", this is difficult, as long

1. The principle of SQL optimization is to minimize the number of blocks that need to be read for an operation, that is, to achieve maximum data throughput in the shortest possible time. Poorly tuned SQL can usually be cut from the following points:?

How to extract a random efficiency from a data table in MySQL, while ensuring the highest efficiency.Method OneThis is the most primitive and intuitive syntax, as follows:SELECT * from Foo ORDER by RAND () LIMIT 1This method works when the amount of

File name: Hello.javaImport java.sql.*;public class Hello {public static void Main (string[] args) {Driver nameString Driver = "Com.mysql.jdbc.Driver";The URL points to the database name you want to access mytestString url = "Jdbc:mysql://127.0.0.1:3

1. To optimize the query, avoid full-table scanning as far as possible, and first consider establishing an index on the columns involved in the Where and order by.2. Avoid null-valued fields in the WHERE clause, which will cause the engine to

Copy the table and copy two data into the new table Create Table like t_comments_sample; #拷贝表结构 Insert into Select * from 1,2; #复制两条数据 MySQL Workbench Execution Procedure Error Error:Workaround:SET = 0; #因为MySql运行在safe-update

Mysql:If you are installing with RPM, check the RPM package:Rpm-qa | Grep-i MySQLIf MySQL is already installed on this computer, it will list MySQL installed files, like Mysql-server Mysql-dev mysql-clientCheck MySQL service:service mysql status,

Select from Group by having Count (*>1Like the above sentence, SQL executes in Oracle, but MySQL does not.However, be aware that it will only return one piece of data. One of the words here is not the final result but one.For example, there are 3

Test table: User has id,name,age,sex field test table: Goods has id,name,price field test table: UG has id,userid,goodsid fieldThe view is really powerful, and here are some of the benefits I've experienced:function One:improves reusability, just

MySQL Slow query configurationMySQL logs all SQL statements that execute more than the set time threshold of the Long_query_time parameter, and the slow query log is the SQL logTurn on Slow Query methodMethod One,In the MySQL config file (under

Perform a change of MASTER to Master_host ..... After error Error 1201 (HY000): Could not initialize master info structure; More error messages can is found in the MySQL error log view log 110830 15:43:01 [ERROR] Failed to open the relay log

Mysql uses small notes such as stored procedures and events [Mark] And mysqlmark Bytes ------------------------------------------------------------------------------------------------[Create a stored procedure and use variables and random

Unveil the secrets of JDBC, so that JDBC is no longer mysterious. 1. What is JDBC? JDBC (Java DataBase Connectivity) java DataBase Connection 2. What does JDBC do?To put it simply, JDBC can do three things: establish a connection with the database,

Mysql Key_buffer_size parameter settings, mysqlkeybuffer In the mysql database, mysql key_buffer_size is the most influential parameter on the performance of the MyISAM table. The following describes how to set the mysql Key_buffer_size parameter

Use of DBubtil, use of DBubtil 1. What is O-R Mapping (Object-link ing) Commonly used O-R Mapping tools Hibernate (fully automated framework) Ibatis (semi-automatic framework/SQL) Commons dbutils (simple encapsulation of JDBC) There are also JPA and