MySQL

The table structure is as follows: Mysql> select * from test; + ---- + ------- + | ID | Name | + ---- + ------- + | 1 | test1 | | 2 | Test2 | | 3 | test3 | | 4 | test4 | | 5 | test5 | + ---- + ------- + Run the following SQL:Mysql>

Generally, secondary indexes are used for count:For example, if ID is PK aid, it is secondary index. Use CopyCodeThe Code is as follows: Select count (*) from table where ID> = 0; Or Select count (*) from table; The results are the same. PK

A power outage occurred during the creation of a table primay key this morning. When the computer started up again, it was found that the MySQL service could not be started. The net start error 1067 was prompted, after two hours, the problem could

It is very important to specify the encoding when creating a mysql database. Many developers use the default encoding, which is difficult to prevent. Coding databases can avoid garbled characters caused by import and export. Webpage data is

MySQL has many storage engines. for different applications, you can select an appropriate storage engine for each table, which helps improve MySQL performance.Create a news table: Copy codeThe Code is as follows: create table 'sandbox'. 'News' ( 'Id'

This article introduces an open-source MySQL database InnoDB data recovery tool, innodb-tools, which extracts table row records from raw data files, restores data from lost or destroyed MySQL tables. For example, if you accidentally execute drop

1. mysql transactions In MYSQL, only INNODB Data Tables support transaction processing. There are two ways to start a transaction: (1)Use begin, rollback, and commit to implement Copy codeThe Code is as follows: begin starts a transaction Rollback

An index is a structure created on a table that sorts values of one or more columns in a database table. The main function is to increase the query speed and reduce the performance overhead of the database system. Through the index, the query data

The mysql password has expired. Today, when I encounter a connection to mysql, the connection is always unavailable, Error 1: An attempt by a client to checkout a Connection has timed out The connection timeout error occurs for the first time.

Join query connects two or more tables according to a certain condition and selects the required data. When different tables have fields of the same meaning, you can use these fields to connect these tables. Reference Table: employee Reference

Balanced data The fixed-length or variable-length string can be used for string type data. The difference is that a string of the fixed length is filled with spaces to the right to ensure the same number of bytes. The variable-length string does not

String operations are a very important component in programming, while string operations in MySQL databases are quite simple. Note that all the following functions do not change the original data only when the modified result is returned. Select a

There are two paging query methods in mysql. One is the COUNT (*) method. The specific code is as follows: Copy codeThe Code is as follows: select count (*) FROM foo WHERE B = 1; SELECT a FROM foo WHERE B = 1 LIMIT 100,10; Another method is to use

The positioning result is as follows: Customer environment:Windows server 2003 r2 standard edition sp2Mysql Ver 14.12 Distrib 5.0.18, for Win32 (ia32)In apache 2.2RisingWebshield client 1.08 The problem has been reproduced. It can be optimized. It

I learned from manual that the mysql_affected_rows function will return abnormal values when the data before and after UPDATE is the same, The following is a convenient solution. The bdobrica at gmail dot com message is displayed on the official

The following is an example of high CPU usage by MYSQL. I hope I will be inspired by my friends who have encountered similar problems. In general, MYQL occupies a high CPU usage, most of which is caused by database query code problems. Too many

Create user information table: Copy codeThe Code is as follows: create table tbl_auth_user ( User_id VARCHAR (10) not null, User_password CHAR (32) not null, Primary key (user_id) ); Insert into tbl_auth_user (user_id, user_password) VALUES

Source: mysqlpub.com MySQL has two functions to calculate the number of rows affected by the previous statement. Unlike SqlServer/Oracle, do not cause functional problems due to this difference: 1. Use the found_rows () function to determine the

One common problem is that the offset of limit is too high, such as: limit 100000,20. In this way, the system will query 100020 entries and then discard all the preceding 100000 entries. This is a very costly operation, the query is slow. Suppose

If you want to import Chinese data, the utf8 Character Set set in mysql will save the UTF-8 character set for the xxx.txt file you want to import. The command load data infile "d: /Websites/Sxxxx/test1.txt "ignore into table 'names' fields