MySQL

In MySQL, the order by and group by are as follows:Select From Where Group Order Note:Group by is executed first than order by, and order by does not sort the group by. If there is only one record after group by, order by will be invalid. To

In web development, we often need to insert data from a table to another table. Sometimes, we also need to specify the import field to import records that do not exist in the target table, although these can be split into simple SQL statements in

Copy codeThe Code is as follows: select *, (2*6378.137 * ASIN (SQRT (POW (SIN (PI () * (111.86141967773438-lat)/360), 2) + COS (PI () * 33.07078170776367/180) * COS (lat * PI ()/180) * POW (SIN (PI () * (33.07078170776367-lng)/360), 2 )))) as juli

In actual development, you always encounter this situation. Or in this case If you are still using select fields from table where like '/%', it is definitely a thankless practice, taking a closer look at the built-in functions of MYSQL is

The Mysql database provides two types of indexes. If they are not correctly set, the index utilization efficiency will be greatly reduced, but the problem is completely unknown. Copy codeThe Code is as follows: create table test ( Id int not

The reason is that the primary key must be unique, that is, there may be duplicates in the database with the current restored database. a restriction that Foreign Keys shoshould be uniquely named throughout the database, an effective method is to

Before starting the installation, first describe the difference between the mysql-5.6.4 and the lower version in the installation, from the mysql-5.5, mysql source code installation began to use cmake, so when we configure the installation directory.

In the development process, you sometimes need to remotely connect to and manage the MYSQL database on another machine. in the implementation process, you may encounter a series of problems, now, we use remote access to mysql data installed on

Apache:If the RPM package is used for installation, the installation path should be in the/etc/httpd directory.Apache configuration file:/etc/httpd/conf/httpd. confApache module path:/usr/sbin/apachectlWeb directory:/var/www/htmlIf source code is

I saw a buddy write a tutorial and record it. I am ready to lose weight at any time. 1. Delete the mysql-test folder; 2. Delete the SQL-test folder;3. Delete the debug folder under the bin directory;4. Delete all files with the. pdb extension in

A temporary table exists when the connection is not disconnected. Once it is disconnected, it does not exist. The data and structure of the temporary table are in the memory. You can perform a test to create a temporary table, but it is not found in

MySql has the corresponding time type in Java.Date java. SQL. Date Datetime java. SQL. Timestamp Timestamp java. SQL. Timestamp Time java. SQL. Time Year java. SQL. Date Analyze itRefer to MySql reference manualDate:A date. the supported range is '2

We know that a large MySQL table with massive records can be divided into several tables based on the primary key, time field, and condition field, or even stored on several servers.The only problem is that cross-server batch query is troublesome

Environment:PC: ubuntu 10.10 192.168.1.112 (master) 192.168.10.245 (slave) MySQL: 5.1.49-1ubuntu8. 1-log The database test already exists in the master. First modify the mysql configuration file:/etc/mysql/my. cnf[Master] # Author: zhxia Copy

BEGIN Declare date_str varchar (8 );Declare table_prefix varchar (20 );Set table_prefix = 'mail _ rare_visit _';Set date_str = DATE_FORMAT (CURRENT_DATE (), '% Y % m % D ');Set @ table_name = concat (table_prefix, date_str );Set @ s = concat

Run the status command to view the Slow queries item. If the value is greater than 0 for a long time, the query execution time is too long. Copy codeThe Code is as follows: Reference content is as follows:Mysql> status; -------------- Mysql Ver 11.18

Mysql 5.5 is installed, and the character set is faulty. The previous mysql servers can be configured in the my. cnf configuration file. However, an error is reported even though this is not the case: At that time, no error logs were configured in

The project needs to re-install a mysql server on the existing server. It is quite difficult, because it was previously tested on my laptop and its system is Ubuntu, what is the path and the startup method. They are all different, so this time I am

When I used the mysql database in my experiment today, I forgot my password and asked me to find it for a long time. Now I want to introduce my own method: I used mysql functions for testing. Copy codeThe Code is as follows: mysql> select user,

In this example, the int char is not given their width, and the system will assign a width to it by default. M indicates the maximum display width. The maximum valid display width is 255. The display width is irrelevant to the storage size or the