MySQL

Recently, a very strange MySQL problem occurs. Using different select statements to query all datasets produces different records. Select * gets four records, and select field gets three records.For details, refer to the following query results:[SQL]

1. Add the primary key (primary key index)Mysql> alter table 'table _ name' add primary key ('column ')2. add UNIQUE (UNIQUE index)Mysql> alter table 'table _ name' add unique ('Column')3. Add an INDEX (Common INDEX)Mysql> alter table 'table _ name'

Assume that the Status field of a data table is of the varchar type and has the following values: NULL, pending, pending refund, refund, and cancel.We know the order whose query status is cancel. The SQL statement can be written as follows: SELECT o.

Mysql Master/Slave configuration note: There are four machines in total: A (10.1.10.28), B (10.1.10.29), C (10.1.10.30), and D (10.1.10.31 ).After the configuration result: the A-C is the master and slave, B is the slave of A, D is the slave of C.0)

The following excerpt describes utf8_unicode_ci and utf8_general_ci In the Mysql 5.1 Chinese manual:Currently, utf8_unicode_ci rules only support Unicode rules. Some characters are not supported. In addition, the combination of tags cannot be fully

A MySQL table can be considered as a queue, with each row being an element. Each query gets the first row that meets a condition, and deletes it from the table or changes its status so that it will not be obtained in the next query. Without

1. Back up data on the Management node.Ndb_mgm> start backup nowaitNdb_mgm> Node 3: Backup 4 started from node 1Node 3: Backup 4 started from node 1 completedStartGCP: 43010 StopGCP: 43013# Records: 2138 # LogRecords: 0Data: 53068 bytes Log: 0

Test Table Structure:Copy codeThe Code is as follows:---- Table structure 'tet'--Create table if not exists 'tet '('Id' int (11) not null,'Name' varchar (255) not null,'Url' varchar (255) NOT NULL) ENGINE = InnoDB default charset = utf8;---- Store

1. How can I change the root administrator password of mysql at the win2K command prompt?> Mysql-u root-pEnter password :******Mysql> use mysql;Mysql> update user set password = password ('new _ password') where user = 'root ';In this way, you can

Records in the error log:[ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql. host' doesn' t existI posted a post. I only saw it, but no one replied. I can only solve the problem by myself. Can I help myself... You don't have to

The following describes several specific implementation methods. The following is the tutorial environment.Mysql> create table tbl (-> Id int primary key,-> Col int-> );Query OK, 0 rows affected (0.08 sec) Mysql> insert into tbl values-> (1, 26 ),->

Table Structure:Mysql> desc demo;+ ------- + ------------------ + ------ + ----- + --------- + ---------------- +| Field | Type | Null | Key | Default | Extra |+ ------- + ------------------ + ------ + ----- + --------- + ---------------- +| Id |

One master and one slave:Master:OS: centos release 5.6 DB: mysql 5.5.8 IP: 192.168.1.2Slave:OS: centos release 5.6 DB: mysql 5.5.8 IP: 192.168.1.3Modify the host Master configuration file (/etc/my. cnf)Copy codeThe Code is as follows:[Mysqld]// At

I have summarized the common methods for determining whether a record exists:SQL statement: select count (*) from tablename;Then read the value of count (*) to determine whether the record exists. The performance of this method is a waste. We just

1. Use the explain statement to view the analysis resultsFor example, explain select * from test1 where id = 1; the columns of id selecttype table type possible_keys key key_len ref rows extra are displayed.Where,Type = const indicates that the

MySQLDatabaseVarcharWhat is the maximum length? In fact, this is not a fixed number. The length of varchar isRestriction rules. In this article, we will introduce the varchar restriction rules in the MySQL database, and describe the restriction

If your configuration file uses a configuration file like a my-innodb-heavy-4G.cnf.Mysql can be started normally, but innodb tables cannot be used.The following output is displayed in the error log:InnoDB: Error: log file./ib_logfile0 is of

Method 1:Select 'name' from mysql. proc where db = 'your _ db_name 'and 'type' = 'Procedure' // Stored PROCEDURESelect 'name' from mysql. proc where db = 'your _ db_name 'and 'type' = 'function' // FUNCTIONMethod 2:Show procedure status; // Stored

After installing mysql, the preparation file should be in the/usr/local/mysql/share/mysql directory. There are several preparation files, including my-huge. cnf my-medium.cnf my-large.cnf my-small.cnf, different traffic of the site and different

Function: FROM_UNIXTIMEPurpose: display the time stored in INT (11) in MYSQL in the "YYYY-MM-DD" format.Syntax:FROM_UNIXTIME (unix_timestamp, format) Returns a string representing the Unix time mark, formatted according to the format string. Format