mysql pivot table

In practice, we sometimes encounter deletion and modification of database tables and databases. The following articles provide solutions to this problem, that is, use the MySQL command to correctly modify some tables and modify the table structure. Use the MySQL command to modify the table and the

When MySql is started in Windows 7, the error Table bitsCN.com is returned. When MySql is started in windows 7, the error Table 'MySQL. plugin 'doesn' t exist solution: 64-bit Windows 7, install mysql5.27 _ win64, and customize the installation to D:/database/

is single table, will make 1 million requests, and now after the table, it is possible to make 10,000 data per table request (because, can not be absolute average, just assume), So the pressure is much lower. Use the Merge storage engine to present a horizontal list of instances: View MySQL 's storage engine

http://blog.sina.com.cn/s/blog_68431a3b0100y04v.htmlMethod 1:TRUNCATE TABLE nameThis will not only delete all the data, but also reposition the increment fieldMethod 2:Delete from your table nameDBCC CHECKIDENT (your table name, reseed,0)Reposition the self-increment field so that it starts at 1Method 3:If you want to save your data, introduce you to the third me

difference is that the table divides the large table into several separate entity tables, while partitioning divides the data into multiple locations, which can be the same disk or on different machines. After partitioning, the surface is still a table, but the data is hashed to multiple locations. When the app reads or writes a large

the following query results:Third, sub-query:Role: In some cases, when making a query, the condition required is the result of another SELECT statement, which is the time to use a subquery.Definition: The query (internal query) executed first to provide data to the main query (external query) is called a subquery. In other words, the subquery is executed first, and then the main query is executed based on the results of the subquery.Keywords: the keywords used for subqueries mainly include in,

MySQL [ERROR] Table 'mysql. user' doesn' t exist, mysql. userexist A newly installed mysql source code, because the my-default.cnf was not copied to the/etc/my. cnf location, when starting mysql encountered an error that could not

MySQL table sharding Methods: MySQL I. Let me explain why Table sharding is required. When a piece of data reaches several millions, it takes more time for you to query the data at a time. If there is a joint query, I think it may die there. The purpose of table sharding is

characters, because character sets and sorting rules make the characters more complex. (3) Avoid NULL as much as possible) The field must be defined as not null as full as possible. Even if the application does not need to save NULL, many tables contain columns that can be empty. This is only because it is the default option, unless NULL is saved, otherwise, the column is defined as not null. It is difficult for MySQL to optimize queries using empty

command requirements for creating tables: The name of the table table field Name Definition of each field Grammar: The following is a common SQL syntax to create a MySQL table: CREATE TABLE table_name (column_name column_type); Now, we will create the following Tutori

MySQL is very powerful, support direct copy database file Quick Backup, where is the database file?Open the MySQL configuration file My.iniand locate the datadir node, asDatadir= "D:/program files/mysql/mysql Server 5.1/data"Enter the above folder, you can see the new database folder in

When a mysql temporary table is working on a very large table, you may occasionally need to run many queries to obtain a small subset of a large amount of data, instead of running these queries on the entire table, instead, MySQL can find a few required records each time, an

values (this is incorrect because it is not supported on the Internet ). Memory tables support operations greater than (>) and less than ( After mysql is restarted, the primary key, auto-increment, and index still exist, but data is lost. This is also used to correct some incorrect texts on the Internet. The memory table is shared among all clients (just like any other non-TEMPORARY

Due to a temporary requirement, you need to add a field to a table of more than 10 million online MySQL databases. This table is fully implemented as required during design and there are no additional Reserved fields. Problem Description Due to a temporary requirement, you need to add a field to a table of more than 10

I believe that you will not be familiar with the operation of copying data from a MySQL table. The following describes how to copy data from a MySQL table to a new table. 1. MySQL copies the