MySQL

Myisam stores data in three files: MYD,. MYI,. FRM, and index files.Innodb stores data including. FRM storage table definition ,. ibd (exclusive tablespace ),. ibdata (shared tablespace ). innodb stores data in standalone and shared tablespaces

To know the size of each database, follow these steps:1. Enter the information_schema database (storing information about other databases)Use information_schema;2. query the size of all data:Select concat (round (sum (data_length/1024/1024), 2), 'mb'

About 0.2 million of data insertion operations were encountered during work. After the program was compiled, it was found that the Operation timed out. The maximum PHP Execution time was modified to 600, or timed out. Check the number of data

When using mysql (show tables), you sometimes need to view the table and field information (whether the table and a field exist .)~~ PHP provides such related functions, such as mysql_list_dbs () and mysql_list_fields (), but the mysql_list_fields ()

In MySQL, you can use Limit to query records from column m to column n. For example:Copy codeThe Code is as follows:Select * from tablename limit m, nHowever,The Limit statement is not supported in SQL Server. What should we do?Solution:Although SQL

Each data access uses its own communication protocol, including calling different interfaces and passing parameters. The information in different databases should be used in the same program. Normally, different database connection methods should be

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'

Different SQL statement writing methods often bring about great performance differences. How can we know the overhead of SQL query execution? MySQL provides the EXPLAIN keyword for us. When you add the EXPLAIN keyword before your select statement,

In some cases, if only one query result is known, using LIMIT 1 in SQL statements will increase the query efficiency.For example, the following User table (primary key id, email address, and password ):Copy codeThe Code is as follows:Create table

The system information function is used to query the system information of the mysql database.VERSION () returns the database VERSION number.Copy codeThe Code is as follows:Mysql> select version ();+ ------------------------- +| VERSION () |+ -------

Search for subdomains For example, jb51.net searches for www.jb51.net, jb51.net, and host.jb51.net. If mysql is used with like, the efficiency is very low. millions or even tens of millions of data cannot be used, so sphinx is used. Many problems

Relational databases depend on primary keys, which are the foundation of the Physical Mode of databases. The primary key has only two purposes on the physical layer:Uniquely identifies a row.As an object that can be effectively referenced by a

In Windows, the following ERROR occurs during mysql Logon: ERROR 1045: Access denied for user: 'root @ localhost' (Using password: YES)I found some solutions from the Internet and finally got a solution. Now I want to record the specific

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> select * from test where id

I,Background In the past, when I used SQL Server to partition a table, I encountered a lot of questions about unique indexes: Step 8: SQL Server. When the table partition encounters a unique constraint, I did not expect this problem to occur in

1. Introduction In the Web application architecture, the data persistence layer (usually a relational database) is a key core component and has a very important impact on the system performance. MySQL is currently the most widely used open-source

Introduction Xtrabackup is a mysql database backup tool provided by percona. According to the official introduction, Xtrabackup is the only open-source tool in the world that can perform hot backup for innodb and xtradb databases. Features:(1) The

Previously thought from top to bottom unified use of UTF-8 on the rest of the peace of mind, which knows today in the capture of Sina Weibo data or encounter character exceptions.An exception is thrown when the data captured from Sina Weibo is

Mysql slow query logs are very useful for queries with tracing problems. We can analyze the resource-consuming SQL statements in the current program. How can we open mysql slow query log records?In fact, it is very easy to open the slow query log of

This is a good mysql database optimization article I have seen on the Internet. The content is full!1. Use indexes to traverse tables faster The index created by default is a non-clustered index, but sometimes it is not optimal. In a non-clustered