MySQL

MySQL supports a large number of column types, which can be divided into three types: Number type, date and time type, and string (character) type. This section first provides an overview of available types, summarizes the storage requirements for

1. check whether the Mysql version supports partition show variables like '% partition % '; + ------------------- + ------- + | Variable_name | Value | + ----------------- + ------- + | have_partitioning | YES | + ----------------- + ------- + if

1. the INNODB Storage engine of background processes consists of four I/O threads, one master thread, and one lock monitoring thread, with one error monitoring thread. The following describes that the innodb_file_io_threads parameter value is 8 and

During the top Shard, The PreparedStatement encountered garbled Characters During database storage, which had plagued the database for a long time and finally solved the problem.The problem code is as follows: [java] pstmt = con. prepareStatement

The usage of explain in mysql has recently encountered some database problems during performance tests. Generally, you can use slow query logs to find SQL statements with poor execution performance, however, it is not possible to find these SQL

Mysql blob's simple learning Blob has the advantage of ignoring the type of stored files. images, files, and compressed packages are stored in binary files;The disadvantage is that if large files (such as multimedia files) are stored, the efficiency

Mysql may encounter the following two problems when importing an SQL file: 1. If the SQL file is too large, the "MySQL server has gone away" problem may occur;2. if the SQL file data contains Chinese characters, the following error occurs:

1. Compared with interface operations, SQL statement operations are more flexible and powerful. Set character_set_client = gb2312; set character_set_results = gb2312; www.2cto.com 2. once the database and table are created, the next step is to

MYSQL time function usage test table: root @ test 16:50> desc t1; + ------- + ---------- + ------ + ----- + --------- + ------- + | Field | Type | Null | Key | Default | Extra | + ------- + ---------- + ------ + ----- + --------- + ------- + | id |

MySQL learning note _ How to choose the appropriate storage engine MyISAM: suitable for use with select and insert-based, with only a few updates and delete, and transaction integrity,Concurrency requirements are not very high. MySQL is one of the

1. Arithmetic Operators arithmetic operators perform mathematical operations on two expressions, which can be any numeric data type. Arithmetic Operators include: + (plus),-(minus), * (multiplication),/(Division), and % (Modulo. (1) The "+" operator

Method 1: SELECT... INTO OUTFILEmysql> select * from mytbl into outfile '/tmp/mytbl.txt'; Query OK, 3 rows affected (0.00 secure1_mytbl.txt contains the following content: mysql> system cat/tmp/mytbl.txt 1 name12 name23 \ N the data in the exported

Several commonly used time functions in mysql check the api documentation each time they write SQL statements about the time. In large space, they can be found in just half a day, to improve efficiency, take the lead in recording several commonly

Summary mysql query comprehensive exercise 0-personal memo Command Line Mode 1. encoding format conversion (the command line is gbk encoding, and mysql must be told to be gbk encoding)2. Insert a table, as shown in3. Obtain the field attribute

Mysql Data backup script [html] # crontab-e #0 2 ***/home/mysql/bak. sh thisday = 'date "+ % G % m % d" 'bakdir = '/home/mysql/bak 'bak_name = $ bakdir/'exp _' $ thisday '. SQL 'mysqldump -- default-character-set = utf8-h 192.168.1.10-u userName-p

Slow query log Slow query statement slow query log Slow query log. By setting related slow query parameters, You can output Slow SQL statements of the database to the log. This is the slow query log, in many cases, due to performance issues, slow

Solve the MySQL classic problem of Chinese garbled MYSQL: (ERROR 1366 (HY000): Incorrect string value: '\ xD5 \ xD4' for column 'name' at row 1) there are a lot of posts on the Internet to solve Chinese Garbled text, basically speaking about

1. Comparison operators: =,>, =, , and ,! =, Here we know <> and! = Meaning is the same. They all mean not equal. Look at your preferences. it is used when the values on both sides of the comparison are NULL, in this case, mysql provides a

The same number adjacent to the MySQL query record time. The record interval is less than the specified number of seconds # create table 'tmp _ 20120710_3 '('id' int (11) not null AUTO_INCREMENT, 'desttermid 'varchar (11) default null, logtime

When mysql is connected to a program, a disconnection may occur if the connection wait time (wait_timeout) is not reached within a certain period of time, which is related to the database configuration. The default mysql connection wait time is (2880