MySQL

When mysql modifies an index, the foreign key constraint causes a strange problem. In mysql5.5 of Windows, I want to modify the index of a table, run www.2cto.com [SQL] ALTER TABLE practice_log DROP INDEX ix_practice_log_userid; ALTER TABLE practice_

How can I delete data from multiple associated tables at the same time when I DELETE multiple table data based on the DELETE operation of another table? Here I have made an in-depth explanation: www.2cto.com 1, delete from t1 where condition 2,

Database Transaction Processing exclusive lock under www.2cto.com make an experiment to verify the effect of the lock Terminal 1, first enter the transaction status and then run the following statement mysql> begin; Query OK, 0 rows affected (0.00

In the MySQL master-slave environment, we can run show slave status on slave to view some slave status information. Among them, there is an important parameter Seconds_Behind_Master. Do you understand the true meaning of it and how it is

When querying multiple database Field names, the results are duplicated. How can I query duplicate database results? When using mysql, you sometimes need to query records with unique fields. Although mysql provides the keyword distinct to filter out

After the primary key generation is configured in Hibernate for Mysql to generate UUID, the primary key generation mechanism is not specified in mysql. When using Navicat to insert data through SQL statements, you still need to specify the Id,

In database design, for a specific project, the same table prefix is usually specified for all data tables, for example, WordPress Data Tables start with wp _ and Discuz Data Tables start with dz. This not only facilitates differentiation, but also

For the question about why limit is slow in the future, we have used mysql paging, the implementation is generally select * from talbe_name limit pageSize * (pageNo-1), pageSize the first few pages of the statement is very fast, why does pageNo

Mysql exists subquery can be divided into: from where and exists subquery www.2cto.com classification table: [SQL] mysql> select * from category; + ---- + --------- + | id | c_name | + ---- + --------- + | 1 | ios | 2 | android | 3 | sb | + ---- + --

In CentOS, mysqlhotcopy is used to regularly back up MySQL databases (MyISAM storage engine). mysqlhotcopy and mysqldump are compared: the former is a COPY in the sense of a fast file, and the latter is a collection of SQL statements on the database.

MySQL index details index is a special file (index on the InnoDB data table is a part of the tablespace), which contains reference pointers to all records in the data table. Www.2cto.com Note: [1] indexing is not omnipotent! Indexing speeds up data

MySQL Proxy-Core layer (Core) Network Core is built on the basis of socket processing implementation, and the client connection and server connection are associated together. [Connection Life Cycle] connection can be in one of the following four

MySQL update nesting when we want to retrieve the data d1 in col1 (for example, the current blog access volume) of column id = 5 from table 1 in MySQL, when the table1 attribute p1 is updated to d1 + 1, we may think of using this SQL statement [SQL]

Mysql's FIND_IN_SET () usage FIND_IN_SET (str, strlist) returns the serial number of str in the strlist of the string set (if any parameter is NULL, NULL is returned. If str is not found, 0 is returned, an exception occurs when parameter 1 contains "

Emma Chinese display garbled problem solved in Linux if you use the mysql graphics client, I personally feel that Emma is not bad. However, if emma is installed with apt-get by default, emma does not support Chinese characters. You need to modify

Mysql checks the index usage. This is a read-based online database. Java code root @ read 02:28:07> show status like 'handler _ read % '; + -------- + --- + | Variable_name | Value | + -------- + --- + | Handler_read_first | 0 | Handler_read_key | 0

Location of the Code involved in the MySQL main process 1. main () in SQL/mysqld. cc 2. the function for receiving the request is: handle_connetions_sockets (), SQL/mysqld. cc 3. request Processing Portal: handle_one_connection (), SQL/SQL _parse.cc

[Mysql] avoids repeated insert records and obtains the id of the duplicate records. Assume that col1 is unique in the tbl column, that is, unique. To avoid duplicate col1 values inserted, you can use the ignore attribute: [SQL] insert ignore...

Flexible handling of mysql Data Import errors is often used to resolve SQL file import to the database. It may be the restoration of the database from the mysqldump script or the database migration. Such an SQL file usually contains many statements.

Ubuntu installation and configuration mysql this article only introduces the simplest and most basic installation and configuration methods 1. install [plain] sudo apt-get install mysql-server during installation, the mysql password is set interface,