MySQL

The date_format and STR_TO_DATE of MYSQL are recently used in the project. Have a good time with the MYSQL date conversion function. The process is as follows: Take the current year: SELECT DATE_FORMAT (CURDATE (), '% Y year'); output: SELECT

MySQL connection timeout automatic disconnection Problem description: when using mybatis2.3.5 for application implementation, the program reports the following error: com. mysql. jdbc. exceptions. jdbc4.CommunicationsException: The last packet

A little understanding of MySQL Character Set Although this article aims to understand, but a little understanding can also, after all, Zhuge Kong Ming is only based on the character value can have the so-called character set concept, some character

This version of MySQL doesn't yet support 'limi... resolving This version of MySQL doesn't yet support 'limit & IN/ALL/ANY/SOME subquery' means, mySQL of this version does not support IN/ALL/ANY/SOME subqueries using the LIMIT clause, that is, LIMIT

MySQL uses the delimiter to import and export records and summarizes the Syntax: Backup: SELECT INTO OUTFILESELECT * FROM hx_9enjoy INTO OUTFILE '/tmp/9enjoy.txt'  By default, fields are separated by tab, and records are separated by \ n. You can

The principle of using hard links to delete large MySQL files in seconds: hard link: when multiple files point to the same inode, inode connections N> 1, deleting any file is very fast, because at this time, only the pointer to inode is deleted, and

For mysql Illegal mix of collations (gbk_chinese_ci, IMPLICIT) and (gb2312_chinese_ci, I solves common garbled issues, some when the database itself is gbk or gb2312, however, the query results are garbled. This is because mysql still has a channel

The server quit without... problem occurs when mysql is started in ubuntu. How does this error occur? Why does The server quit without updating PID file (.... pid. cnf 2: Permission issue for the/usr/local/mysql/data folder 3: The mysql service

The following describes how to solve the Mysql data rollback error. You can refer to the following two methods for MYSQL transaction processing. 1. Use begin, rollback, and commit to start a transaction rollback transaction to roll back the commit

MySQL field constraints: null, not null, default, auto_increment in MySQL, each field definition contains additional constraints or modifiers, which can be used to add constraints on the input data. Today, let's take a look at the MySQL field

The concat () function can concatenate strings in SQL statements. In mysq, this function can concatenate multiple strings, you can also connect two or more arrays. The following is an example, he can concatenate the string and the queried field into

Load data infile: import millions of pieces of data in the excel file into the database in MYSQL within one minute, and use the load data infile command. Step 1: Save the excel file as a csv text. csv files are separated by commas (,). 2. Enter an

To modify the max_allowed_packet attribute of MySQL 5.5, the following error is reported when an experiment system is deployed: your 'max _ allowed_packet 'variable is set to less than 16777216 Byte (16 MB ). it is easy to understand, that is, you

In MsSQL, commands similar to MySQL replace into remember a case in which MySQL was used many years ago. At that time, a requirement was raised when an additional item was added to the data table, determine whether the cursor exists. If the cursor

MySQL SQL statements that programmers use are only practical. MySQL SQL statements that programmers often use (excluding basic select, update, and delete statements ). 1. add a user build and grant all permissions to the command [html] grant all

Mysql operator (job) Create Table tmp15, including varchar type field note and int type field price, use the operator to calculate different fields in the table; use logical operators to perform logical operations on data; mysql> create table tmp15 (

Add, delete, modify, and sort table fields in Mysql 1. Create a new table with the following fields: Student ID, name, and age. Mysql> create table new (ne_id int (10), ne_name varchar (20), ne_age int (12); Query OK, 0 rows affected (0.97 sec) 2.

Mysql does not use index exceptionsMysql index today finds a strange thing about mysql: Table Structure:Table index:We can see that the ver is of the varchar type and has an index. Search for a piece of data that does not exist:The type is actually

MYSQL stored procedure Result consisted of more than one r... Abstract: MYSQL Stored Procedure error SELECT... INTO... This SELECT syntax stores the selected columns directly to variables. Therefore, only a single row can be retrieved. Note that

Mysql ifnull function uses mysql ifnull (expr1, expr2) If expr1 is not NULL, IFNULL () returns expr1, otherwise it returns expr2. IFNULL () returns a number or string value, depending on the context in which it is used. [sql] mysql> select IFNULL(1,0