Pt-Online-schema-change of MySQL online DDL Tool

Pt-Online-schema-change of MySQL online DDL Tool MySQL DDL:DDL is a feature that makes all MySQL ddbas criticized, because in MySQL, when dDDL is performed on a table, it locks the table. When the table is small, such as less than 1 W rows, it has

MySQL query plan key_len all know

MySQL query plan key_len all know This article first introduces the meaning of ken_len In the MySQL query plan, then introduces the calculation method of key_len, and finally uses a forged example, to show how to use key_len to view the number of

MySQL Tutorial: Use tpcc-mysql for stress testing

MySQL Tutorial: Use tpcc-mysql for stress testing Tpcc-mysql is a product derived from tpcc for mysql Benchmark Testing. For more information, see high-performance MySQL 3. I. Installation Rpm-Uvh

Enumeration of common MyCAT sharding rules

Enumeration of common MyCAT sharding rules MyCAT supports multiple sharding rules. In the following example, partition enumeration is used. In applicable scenarios, the number of column values is fixed, such as province and month. Here, three values

Use SQL statements to repair SQL Server databases

Use SQL statements to repair SQL Server databases When using the SQL Server database, some small errors may occur in the database due to power failure or other reasons, such as the slow retrieval of some tables and the failure to query Qualified

MySQL Tutorial: I/O Memory Optimization

MySQL Tutorial: I/O Memory Optimization Mysql Ver 14.14 Distrib 5.6.19, for Linux (i686) using EditLine wrapper I. mysql directory files Ibdata1: The system tablespace contains data dictionaries, rollback logs, and undolog. (Insert buffer

MyCAT Log Analysis

MyCAT Log Analysis MyCAT logs cannot be obtained for running information about MyCAT. For example, if MyCAT adopts read/write splitting, how does MyCAT execute a query statement, and which node each shard is distributed. The default value is the

Create an Oracle 12c user

Create an Oracle 12c user Oracle 12c accounts can be divided into public accounts and local users. A common account is created under CDB and can be used by all PDB users. A local account can only be created in PDB. Create a public userAlter session

Practices for restoring data using MySQL binlog

Practices for restoring data using MySQL binlog A few days ago, I worked overtime until. On the way back, a friend called and said that the development and maintenance staff of their company were updating the online system versions, accidentally

MySQL Tutorial: About the checkpoint Mechanism

MySQL Tutorial: About the checkpoint Mechanism I. Introduction Think about this scenario: If the redo log can be infinitely increased and the buffer pool is large enough, you do not need to refresh the new version of the page in the buffer pool to

SQL Server automatic backup script

SQL Server automatic backup script SQL Server backup script: Third-party backup, and differential backup at other times. declare  @device  varchar (30); declare  @filename  varchar (50); declare  @datetime  varchar (50);

Oracle 11g installation diagram and related dependent libraries in SUSE 11

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MySQL import of large data volumes

MySQL import of large data volumes First: in fact, the best way is to directly use: Mysqldump-u username-p Password Database Name In Linux, we tested an imported data of over 10 thousand rows, totaling 121 MB. In Linux, the import is successful

Saving Oracle learning database data as files

Saving Oracle learning database data as files It is often necessary to generate documents from data in Oracle databases. Because you prefer the script method, you need to set the format when using spool, the following is a simple example of how to

Verification of the MyCAT Character Set

Verification of the MyCAT Character Set The default Character Set of MyCAT is UTF8. The following describes how to check the log to verify the effect of different MySQL client character sets and server character sets on MyCAT. There are three main

Solve the Problem of invalid Oracle environment variables in Linux

Solve the Problem of invalid Oracle environment variables in Linux When you maintain the Oracle database in Linux today, view the listener status and execute # Lsnrctl status Error:-bash: lsnrctl: command not found. This is not the case in the

MySQL-related statements (add, delete, modify, and query) (SQLyog software implementation)

MySQL-related statements (add, delete, modify, and query) (SQLyog software implementation) MySQL-related statements (add, delete, modify, and query) (SQLyog software implementation) -- Create an employee table: empCreate table emp (Empno INT, --

Oracle: RETURNING clause

Oracle: RETURNING clause RETURNING is usually used in combination with DML statements. (Insert update delete) Usage: UPDATE table_name SET expr1RETURNING column_nameINTO xxx INSERT: returns the added value.UPDATE: return the updated value. DELETE:

Difference between Having and Where in SQL, sqlhavingwhere

Difference between Having and Where in SQL, sqlhavingwhere Description Where Select before grouping Having Having can select an aggregation function only after grouping.Eg: // Select count (*) from awhere a. a1> 0 group by a2; // However,

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