default null

Mysql optimization 1 (20170703), mysql optimization 20170703 1. Table Structure Create table 'room _ break_history_tmp_test '('Id' INT (11) not null AUTO_INCREMENT,'Break _ type' INT (11) default null,'App _ id' INT (11) default null,'Room _ id' INT

1. Logic meaning of varchar (N)From MySQL4.1, N in varchar (N) indicates the maximum number of characters (characters) that can be stored in this field, not the number of bytes.Whether it is a Chinese character or a number, or a Chinese character,

The demand now has such a requirement: mysql has a table, and the data is growing fast. However, the data validity period is one month. The record a month ago is not very important, but cannot be deleted. To ensure the query speed of this table, a

[Mysql] backing up the insertinto .. select history of a table in the same databaseRequirement Now there is such a requirement that mysql has a table and the data grows fast. However, this data is valid for one month, and the record a month ago is

Summary: MySQL searches for duplicate rows and retains a record of the duplicate data according to certain conditions:     In the first case, the condition for determining whether the record is retained is a primary key or a unique value   ----

root@22:17:26 [hmda]> ALTER TABLE txt_register add httpheaderinfo varchar (5000) DEFAULT ' NULL '; ERROR 1067 (42000): Invalid default value for ' CurrentTime ' Look at the next currenttime is datetime ROOT@22:17:33 [hmda]> Show create TABLE

[Top] Spring Security3.1 Latest Configuration InstanceCategory: Spring 2011-04-28 11:21 72171 People read review (159) Collection Report Security Spring resources Null Interceptor Object These days to learn spring Security3.1, from the official

/*Navicat MySQL Data TransferSource server:206 Docker MySQL 13306Source Server version:50720Source host:192.168.7.206:13306Source Database:kafkamonitorTarget Server Type:mysqlTarget Server version:50720File encoding:65001Date:2018-05-05

Create a Init.sql file in the SQL folder under Src/main/resources, and put the build table statement:CREATE TABLE {DB}. ' Agent_status ' (' Device_num ' varchar (+) not NULL,' Start_time ' timestamp not NULL the DEFAULT current_timestamp on UPDATE

From: http://citszhanghj.spaces.live.com/blog/cns! D7f04e581faf210! 390. Entry Struts + hibernate + MySQL Chinese garbled Solution 1. Modify the my. ini configuration file of the MySQL database,# Client Section #--------------------------------------

The two tables are a one-to-many mapping relationship, and errors that occur when a foreign key constraint is established in the table. As long as the table when the corresponding foreign key constraints removed it is OK. Two tables are: CREATE

　　There is a concept of storage engine in MySQL and the optimal storage engine can be selected for different storage requirements.I. OverviewMySQL 5.0 supports storage engines including MyISAM, InnoDB, BDB, Memory, MERGE, EXAMPLE, NDB Cluster,

1 Utl_file Package IntroductionOracle's Utl_file package is used to implement I/O operations on disk files.(1) The previous version of oracle10g needs to specify the directory that the Utl_file package can manipulate.Method:1, alter system set

Allow local access port: Iptables-p OUTPUT ACCEPT1. Yum install MySQL2. Yum Install Mysql-server3, delete the user table in the MySQL database user is empty records;4. Execute the following SQL statementUse MySQL;mysql> UPDATE user SET

Take the common user table, the article Class table, the log table to analyze the following CREATE table ' user ' (  ' id ' int (one) unsigned not NULL auto_increment COMMENT ' user ID ',  ' Name ' varchar (255) NOT null COMMENT ' user name ',  '

1. Execute the SQL file:Source/usr/local/crazy/file/test.sqlShow tables; --Show all tables in the databaseNote: You need to put the SQL file in a folder on the server, you can not have a Chinese directory, or do notDrop database name; --delete

Reference documentshttp://nlp.solutions.asia/?p=362http://blog.csdn.net/fby98710/article/details/10367175http://blog.csdn.net/itufo/article/details/21519593Environments that require jdk1.71. mysql Database configurationL My.ini ConfigurationAdd

This article mainly explains the mysql commands in centoslinux (redhatlinux). If your mysql is installed in source code, I add the "mysql installation directory bin" to the path environment variable, mysql startup script has been copied to etcinit.

1. query the log records of one hundred tables. Implementation Using Stored Procedures and cursors Declare @ tablename varchar (32)Declare @ SQL varchar (8000)-- Set @ SQL = 'select * From user_table1'Declare mycursor cursor for -- Define a

The raw type is a data type that is used in Oracle to hold a bit string, similar to char, declared with a raw (L) method, up to 32767 bytes long. The system provides a SYS.UTL_RAW toolkit for raw type operations, and the commonly used functions are