MySQL

MYSQL conversion coding solution 1. Obtain the hexadecimal encoding mysql> SELECT hex (CONVERT ('tourists' USING gbk) under gbk of the Chinese 'tourists' in mysql of utf8 )); -> D3CEBFCD www.2cto.com reversed gbk hexadecimal encoding and retrieved

A mysql database query performance problem encountered this week. Similar to the following simple query in a MYSQL table, it takes nearly one second. The table www.2cto.com 1 select sum (col5), sum (col6) from table_name2where col_key_2 = 'value1

MYSQL: Use UPDATE to modify the user name and cannot log on. 1. create a user test/test www.2cto.com [SQL] mysql> create user test identified by 'test'; Query OK, 0 rows affected (0.00 sec) mysql> exit Bye 2. Use the test/test user to log on

Use float data in databases with caution. Most programming languages Support float or double data types. The database also has data types with the same keywords. Therefore, many developers naturally use float as the field type where floating point

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

Mysql slimming method Note: 1. before performing this operation, stop the Database Service and copy the mqslq5 folder for backup. install the Database Connection Tool navicate on the computer where the database is located; 3. delete useless

Mysql prefix index Application Scenario: There is an address field in the database, the type is varchar (100), the business determines the need to often based onAddress. Determine the Selectivity of www.2cto.com: SQL code SELECT count (DISTINCT

Mysql trigger jumps out of the current loop method set @ num = @ UnitLength/3; label: while I Type = 'smscall' and unit_sid_fk = @ length); set @ sms_counts = (select sms_counts from sms_config where sms _Type = 'smscall' and unit_sid_fk = @ length);

Mysql: the most practical SQL statement 1. replace 0 2. ADD an alter table 'isc _ product_tags' ADD 'bigtags' VARCHAR (20) (1) to the TABLE to delete excessive rows www.2cto.com delete FROM 'isc _ product_ta Gs 'where' tagname' = ''3. delete TABLE

Mysql merges the content of a certain field in the same table. mysql> create table t (id int, name varchar (20); Query OK, 0 rows affected (0.09 sec) www.2cto.com mysql> insert into t values (1, 'A'), (1, 'bb'), (2, 'cc'), (2, 'dd '); query OK, 4

MySQL Master/Slave separation master database configuration 1,/etc/my. cnf master database configuration # generally, www.2cto.com server-id = 1 # Database binlog-do-db = search # Database replicate-ignore-db = that does not need to be copied

Mysql SQL statement optimization common mistakes: www.2cto.com misunderstanding 1: count (1) and count (primary_key) are better than count (*) Many people use count (1) to count the number of records) and count (primary_key) instead of count (*),

A few days before mysql cross-Table deletion, I wrote a summary of Mysql cross-Table update. Today we will look at cross-Table deletion. After www.2cto.com and Mysql4.0, mysql began to support cross-Table delete. Mysql can delete multiple table

In linux, mysql encoding is set. in Linux, after logging on to mysql by default, show variables like '% character %' appears. mysql> show variables like '% character %' appears '; -------------------------- | Variable_name | Value | Modify/etc/mysql/

Ubuntu thoroughly remove MySQL reinstall MySQL 1. Delete mysql sudo apt-get autoremove -- purge mysql-server-5.0 sudo apt-get remove mysql-server sudo apt-get autoremove mysql-server sudo apt-get remove mysql -common // This is very important 2.

Table 'mysql. servers 'doesn' t exist and not allowed to connect to MySQL server solve the problem of installing wamp at home today. After installing wamp, the default mysql root Password is blank. After changing the password flush privileges, the

Net start mysql starts mysql and prompts a system error. 5. How can I solve this problem? After some consideration, I found the cause because the current user's operation permission is too low and an error occurs. The screenshot is as follows:

To monitor slow execution of Mysql statements, you must first enable the log_slow_queries authority for slow query output. You can set it in the MySQL configuration file (my. ini/my. cnf) or through the MySQL client. The advantage of the second

Personalized settings MySQL prompt Interview 4 methods (I) modify the MYSQL_PS1 variable at the Bash layer [plain] [root @ localhost ~] # Export MYSQL_PS1 = "(\ u @ \ h) [\ d]>" [root @ localhost ~] # Mysql-u root-p Enter password: Welcome to the

MySQL: Basic Order by & Limit sub-clause 1. using basic 'order by 'java Code # order stu by stu_score as the Order of descendant select * from stu order by stu_score desc; 2. using 'ORDER BY' to order multiple columnsJava Code # order table 'std' by