MySQL

Avoid editing dump files The dump file created by mysqldump is inherently harmless, but it's easy to try to edit. However, one should be aware that in any case an attempt to modify these documents proved to be dangerous. Visually altering these

In this article I will discuss a related topic –INNODB transaction isolation mode, as well as their relationship to MVCC (multiple versioning concurrency control) and how they affect MySQL performance. The MySQL manual provides a proper description

A one-to-many list of two tables, typically a foreign key of a table, is associated with the primary key of another table. But there are also unusual situations where two tables are not associated with a primary key in one of the tables. For example:

The following is an example of the CPU-intensive processing of MySQL, hoping to be a bit of a inspiration to friends who encounter similar problems. Generally speaking, MYQL occupies a high CPU, most of the database query code problems, too much

MySQL update some of the data in the field in the first case: Copy Code code as follows: Update tab SET A = concat (substring (a,1,3), ' BBB '); Starting with the 1 characters of a, 3 characters, plus ' BBB ', and writing to a, if a

1> query data table except the first three data. At first, I thought of this statement. SELECT * FROM admin WHERE userid to (select UserID from admin order by UserID LIMIT 3) Order by UserID DESC But the runtime will report this version of MySQL

The database is recorded in the table table by inserts, updates, and deletes, where INSERT statement Implementation inserts data UPDATE statement implementation updates data DELETE statement implementation deletes dataReference table Insert

System Information function to query the MySQL database system InformationVersion () returns the database edition number Copy Code code as follows: Mysql> SELECT VERSION (); +-------------------------+ | VERSION () | +-----------

Today from Windows to export a SQL execution file, and then poured into the unbutn, the results appear garbled, toss 7-8 minutes, Resolution method When you export the MySQL SQL execution file, specify the encoding format: Copy Code code as

There is a Linux server, the system is CentOS system. The web site suddenly does not connect to the database, so friends directly restart the server. In CLI mode, perform service MYQSLD start discovery or Prompt "MySQL Deamon failed to start"

Overview Many times, we need to know what SQL statements MySQL has executed, such as when MySQL is injected, need to know what hurt, and so on. As long as there is a record of the SQL statement, you can know the situation and make countermeasures.

Recently, the development of the project to pick up the MySQL, in the construction of the environment encountered in the Chinese garbled problem. Let me share my solution with you. 1, through show VARIABLES like ' character_% '; Show all the setup

MySQL has 5 million data, but most of it is repetitive, true on the 1.8 million, so want to how to get these duplicate data out, find a lap on the internet, a lot of it is not in such a code, so inefficient, their own pondering a combination of,

The sequence is a set of integer 1,2,3 ... The order in which the builds are generated. Sequences are frequently used in databases, because many applications require that each row in a table contains a unique value and sequence that provides an easy

A database index is a data structure that increases the speed of an operation, in which one or more columns can be used, providing a basis for two quick random lookups and efficient sequential access records to create the index. When you create an

To create a database using mysqladmin: Special permissions are required to create or delete a MySQL database. Therefore, suppose that with root user access, you can create any database using the MySQL mysqladmin binary.Example: Here is a simple

Use the MySQL CONCAT () function to concatenate two strings to form a single string. Try the following example: mysql> SELECT CONCAT (' A ', ' SECOND '); +----------------------------+ | CONCAT (' A ', ' SECOND ') | +-------------------------

Today, I saw a very representative of the optimization case, here is a note to make a mark, to commemorate the casual field definition of the problem. Recall that in the design of the table many people used to design the structure of the table into

MySQL introduced a rename database operation in 5.1, but did not support this command after MySQL5.1.23. Can be said to be an experimental function, not in the production support (mysql-5.1 release in mysql-5.1.30), then in production we sometimes

Today, I received a call from a friend who said that the database was changed by others, and the problem of incorrect data appeared. After a long time, the data type has overflowed (the version of the problem is MySQL 5.1).　Later, through the friend