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has two values.'A','B'Now I want to add a value for it.'C'So there is a modification statement: ALTER TABLE `table` MODIFY COLUMN `type` enum('a','b','c'); How long does it take for me to execute the preceding statement? I mainly want to know that because this field does not involve indexes, does the modification time have to be related to the records of the table
modification is related to the 1000w record of the table. Everyone help me to estimate, I have a plan for downtime, thank you! I've been looking at high-performance MySQL (third edition) recently, and that's what it says. Modify column causes the table to be rebuilt (the internal implementation is to build a table w
Label:1.MySQL generates SQL to delete tables that meet the criteria: 1 select CONCAT ( ' DROP TABLE ' 4 GROUP_CONCAT (table_name), 5 ‘;‘ 6 ) as statement 7 from 8 INFORMATION_SCHEMA. TABLES 9 where 10 table_schema = ' testmybatis ' 11 and table_name like ' table_mo_% '; DROP TABLE table_mo_tt1,table_mo_tt222; Execute the generated s
There are several ways for Mysql to avoid table full errors: ? You are using a MySQL server lower than Version 3.23, and the "in memory" temporary table exceeds the tmp_table_size byte. To avoid this problem, you can use the "-O tmp_table_size = val" option to increase the size of the temporary
MYSQLCLUSTER7.2 + 5.5 create disk table and memory table bitsCN.com Mysql cluster 7.2 + 5.5 CREATE a disk TABLE and a memory table create a memory TABLE and a disk TABLE on the
Tags: aggregation min () go to heavy mysq name strong technology share count () andSingle-table query syntax: Select field 1, Field 2 ... from table nameWhere conditionGroup BY FieldHaving screeningORDER BY FieldLimit Limit number of bars keyword priority: from > where > Group by >Having > Select > distinct > order by >limit; 1. Find the table: from 2. Tak
(Mysql) how to determine whether a numeric variable is included in a table field and list all data in the table containing the variable. if the table contains the following idcsite fields .... 11,2, 13 .... nbsp; 22,3, 4 (mysql) how to determine whether a numeric variable i
Tags: Blockchain blog garbage operation efficiency is the from mode partRecently in the blockchain to make a token of the app, involving the database table in the deletion of records, if a strip delete that is really tiring. Consider directly entering MySQL directly to empty the table or delete the data in the table.This article records the difference between the
Mysql lock table mechanism analysis bitsCN.com in order to better optimize mysql in high concurrency, it is necessary to understand the lock table mechanism when mysql queries an update. I. Overview MySQL has three levels of l
Table A {id, userId, logTime} Table B {id, userId, dimension mentid, updateTime} Table A is the data record Table B, which is equivalent to the historical record table (dimension mentid of userId before updateTime) currently, table
After mysql is upgraded, Tableamp; #39; mysql. serversamp; #39; doesnamp; #39; texist bitsCN.com is reported to solve Table 'MySQL. servers' 'doesn' t exist. One thing I encountered today is that after upgrading the mysql database, I entered the data to create a remote user
How can I return only the content of one table when using mysql multi-table joint query? This article will introduce in detail. For more information, see How can I return only the content of one table when using mysql multi-table
MySQL learning notes-data definition table constraints, paging method summary, mysql learning notes This article describes the data definition table constraints and paging methods of MySQL learning notes. We will share this with you for your reference. The details are as fol
Label:There are three ways to view the MySQL table structure:1, DESC tablename;For example:To view the Jos_modules table Structure command:Desc Jos_modules;View results:mysql> desc jos_modules; +------------------+---------------------+------+-----+---------------------+----------------+ |Field|Type| Null | Key | Default |Extra| +------------------+--
MySQL Reference Manual-obtain the database and table information to ensure that you are connected to the server, as discussed in the previous chapter. In this way, no database is selected for work, but that is good. From this point on, I know a little about how to make a query, which is more important than jumping to create a table, load data for them, and retrie
In mysql, if we want to perform full table copy on the data, in addition to importing and exporting data, we can also directly use commands to perform operations, which can help us with some special operations, such: the table structure can be copied when data is sharded. In mysql, if we want to perform full
MySQL may use temporary tables when executing SQL queries. Generally, using temporary tables means low performance. MySQL temporary tables can be divided into: Memory temporary tables and disk temporary tables, Disks MySQL may use temporary tables when executing SQL queries. Generally, using temporary tables means low performance.
This article mainly introduces the solution to the MYSQL lock table problem, and analyzes the common situations and corresponding solutions of the MySQL lock table problem in the form of instances, for more information about how to solve the MYSQL lock
Mysql imports and exports the table structure and table data and executes the SQL file. Execute the SQL FILE command in mysql: source d: \ myprogram \ database \ db. SQL; Connect to MYSQL: mysql-h host address-u user name-p User p
Verify MySQL master-slave consistency (pt-table-checksum pt-table-sync) Percona-toolkit-2.2.8-1.noarch.rpm has two tools to verify MySQL master-slave Data ConsistencyInstalling tookkit requires some dependent packagesYum install perl-DBI perl-DBD-MySQL perl-IO-Socket-SSL pe
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