MySQL

1. MySQL adds a time interval for the date: date_add () Set @ dt = now (); Select date_add (@ dt, interval 1 day);-add 1 day Select date_add (@ dt, interval 1 hour);-add 1 hour Select date_add (@ dt, interval 1 minute);-add 1 minute Select date_add (

  Create function Time_Span_of_minutes ( Start_day DATETIME, End_day DATETIME) RETURNS FLOAT BEGIN -- Returns the interval between two periods calculated by minute. It is calculated by the method of approaching each day. The value is calculated by 8

  I have encountered some trouble today. Although it has not been solved, I am reminding you. Today, the username created with Grant is "DanielW", and the logon password is incorrect. Create a new one. The username is "Daniel @ localhost", that is,

Today, I just learned about the mysql command in the group to view the maximum number of processes opened. Let's take a look at it ~ Cat/proc/27095/limits | grep "Max open files" Command to view the maximum number of processes opened in mysql How

Let's take a look at the advantages and disadvantages of the three mysql lock mechanisms today:MySQL storage engines use three types of locking mechanisms: Row-level locking, page-level locking, and table-level locking. Next we will analyze the

I always thought that the two functions serve the same purpose. Some differences have been found through simple tests. Admin Mysql> select * from admin; + ----- + ----------- + --------- + | Uid | name | pass | + ---- + ------------ + --------- + | 1

There are a large number of MyISAM log tables in the data center that need to be cleaned regularly. This is set to be done every weekend, about 10 Gb, 5-10 minutes.The event will not be written here, And the stored procedure will be directly stored .

Database data volume surges. Compared with databases similar to other services, the data volume of a table is abnormal. Finally, a duplicate data migration bug is identified...  120301 17:30:43 [ERROR] Column count of mysql. db is wrong. Expected 22,

1. What is an index? Indexes are used to quickly search for records with specific values. All MySQL indexes are saved as B-trees. If no index exists, MySQL must scan all the records of the entire table from the first record until the required

Mysql-hxx-uxx-pxx-e "query statement" db> file example: mysql-h127.0.0.1-uroot-p000000-e "select * from a" test> 1.txt host ip user password query statement database filename: mysql-h127.0.0.1-uroot-p000000-N-e "select * from a" test> 1.txt host ip

The Mysql server cannot be started. The error log prompts:^ G/usr/local/mysql/bin/mysqld: File '. /mysql-bin.000013 'not found (Errcode: 13) 120415 8:59:10 [ERROR] Failed to open log (file '. /mysql-bin.000013 ', errno 13) 120415 8:59:10 [ERROR]

Mysql Korean Garbled text because the database I created contains Korean, I would like to talk about Korean Garbled text here to solve the problem. Other Asian languages are similar. I have summarized the following steps (the red font can be

I have never used a MySQL stored procedure before. I am not used to writing a lot of data for the first time. The record is as follows: The following is the simplest MySQL stored procedure to add two numbers. Note thatSQL code delimiter $ create

Mysql group_concat () function traps my colleague sent me a rest interface today saying there should be data, but no data was found. Solution: After troubleshooting, we found that mysql's group_concat () function only returns a 1024-length string by

Environment for adding Foreign keys to Navicatfor Mysql: NavicatforMysql 8.2 + MySQL Sever 5.1Problem: Add a foreign key to NavicatforMysql:Method 1: use an SQL statement to create a foreign key: [SQL] alter table foreign key table add constraint

MySQL sets the unique key environment: NavicatforMysql8.2 + MySQL Sever 5.1 problem: MySQL graphic setting unique key solution: this function is not available in graphical tools. You can use SQL commands. 1. modify a TABLE, for example, [SQL] ALTER

In an SQL statement that is joined by a Mysql ON clause and a USING clause in Mysql, the syntax FORMAT OF THE ON clause is table1.column _ name = table2.column _ name. When the columns in the pattern design couplet join table adopt the same naming

Gb2312_chinese_CI: Only simplified Chinese characters are supported. Gb2312_BIN: While gb2312_bin is a subset of gb2312_chinese_ci, And gb2312_BIN is binary storage. Case Sensitive The database encoding format has different meanings. Gbk_chinese_CI

MySQL 5.5 has added SIGNAL Exception Handling. MySQL has been supporting stored procedures since MySQL 5.0 and has been in the latest version 5.5 for several years. Although the exception handling in MYSQL is not perfect, it is sufficient to handle

We all know the statements used to connect to MySQL in the LAN are jdbc: MySQL: // localhost: 3306/database, but when you want to connect to mysql on other machines, it is useless to change the localhost of the preceding statement to the