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  Mysql master-master-slave experiment

  Implementation structure: prerequisite, this is a new installation of mysql server, already running mysql needs to make spare parts, and restore to another machine. Master A:192.168.168.128master B:192.168.168

  2022-06-01 13:24:24 Views: 232
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  Sql finds all the record data that are duplicated in a table

  There are two fields in the table, id and name, to query all the data duplicated by name. Now the following is listed: select * from xi a where (a.username) in (select username from)

  2022-06-01 13:24:24 Views: 218
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  Chapter II Summary and aggregation of data (1)

  To fully understand the aggregate function of Oracle, we also need to know what happens when the data contains NULL. Sales rewards are available only to sales staff, but not to non-sales staff, so the COMMISSIO of non-sales staff is reflected in the HR.EMPLOYEES table.

  2022-06-01 13:24:24 Views: 296
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  Oracle datafile generates query tree

  SELECT DECODE (file_name, 'file_name, tablespace_name, LPAD ('-- >', 5) | | file_name) tablespace_name FROM (S)

  2022-06-01 13:24:23 Views: 217
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  CentOS 7.2 mysql-5.7.17 source code edit installation operation, primary primary cluster, database backup script

  The mysql tar source code edit installation operation in the following operating system is CentOS 7. 2 MySQL version mysql-5.7.171. Install yum-y install gcc gcc-c++ ncu according to the package before installation

  2022-06-01 13:24:23 Views: 284
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  Summary of mysql performance Optimization configuration

  Read some books on optimizing mysql operation and maintenance. Under the summary of this record: enter the mysql client and enter the following sql:1, connection setting show variables like'% max_connection%';show statu

  2022-06-01 13:24:23 Views: 220
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  There is no scott.sql file solution for oracle11G.

  The solution when oracle11G does not exist under $ORACLE_HOME/rbdms/admin/ and scott.sql does not exist: su-oraclecd $ORACLE_HOME/rbdms/admin/sqlpl

  2022-06-01 13:24:23 Views: 228
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  Points to be paid attention to in oracle sorting

  The sorting algorithm is divided into stable sorting and unstable sorting. In general, unstable sorting has a lower time complexity. In oracle, you should also note that the sorted result set may not be the target result set. 1, no collation select * from t order by s specified

  2022-06-01 13:24:22 Views: 249
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  Too many mysql connections occupied by Mycat

  Background: mariadb,mycat middleware. Problem: too many DB connections; developers and users use connection pools and even mycat;DB items to be optimized: interactive_timeout,wait_timeout is the 8-hour default. M

  2022-06-01 13:24:16 Views: 233
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  MongoDB sharding fragmentation

  Background when MongoDB stores large amounts of data, one machine may not be enough to store data, or it may not be enough to provide acceptable read and write throughput. At this time, we can split the data on multiple machines, so that the database system can store and process more data. 1 、 MongoDB

  2022-06-01 13:24:10 Views: 212
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  Revealing the secrets of Spring architecture-event monitoring mechanism

  1. Overview of event monitoring mechanism 2. Structure of event monitoring mechanism 3. Spring monitoring mechanism architecture Spring Application has the ability to publish events and register event listeners, and has a complete set of event publishing and monitoring mechanisms. In Java, through jav

  2022-06-01 13:24:10 Views: 205
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  Amoeba implements mysql read-write separation + master-slave replication architecture

  Environment system: centos6.5mysql version: mysql5.6master server: 192.168.1.21slave server: 192.168.1.100master write slave read II, implement mysql

  2022-06-01 13:23:59 Views: 239
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  SQL Server insider data page

  A data page is a structure that contains user data that has been added to a database table. As mentioned earlier, there are three kinds of data pages, each of which stores data in a different format. SQL server has inline data pages, row overflow data pages, and LOB data pages. Compared with SQL server

  2022-06-01 13:23:50 Views: 288
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  Install ORACLE_11G_R2 in SUSE_11_X64_SP4 environment

  First, preparation: the configuration of 1.IP set to static 2./etc/hosts file must be consistent with native ip information. 3.SUSE_11_X64_SP4 system environment 4.ORACLE_11G_R2 installation package: linux.x64_11gR2_

  2022-06-01 13:23:23 Views: 222
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  Group query after mysql filtering

  Syntax: select grouping function, column (required to appear after group by) from table where.. group by grouped list order by. # case: query the average salary of each department SELECT AVG (

  2022-06-01 13:23:23 Views: 227
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  MYSQL (II) Database clustered / nonclustered indexes, indexes and locks

  The clustered index (InnoDB, using B+Tree as the index structure) holds the b-tree index and data rows in a structure; it is stored on the leaf page in the order of the primary key; primary key index: the leaf node stores key-value as secondary (primary key data: all remaining column data)

  2022-06-01 13:23:23 Views: 247
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  The function and usage of MySQL stored procedure DELIMITER

  Stored procedure is a code segment, in the mysql execution process, encountered the semicolon on the execution, how to change the semicolon, let the code continue to execute, the following talk about the role and usage of the MySQL stored procedure DELIMITER. 1JI MySQL stored procedure DELIMIT

  2022-06-01 13:23:23 Views: 298
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  ORA-16629: database reports a different protection

  Oracle 12c RAC- single instance alarm is as follows: DGMGRL > show database verbose coredb;Database-coredb Role: P

  2022-06-01 13:23:23 Views: 287
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  Mariadb database service

  What is mariadb? MariaDB database management system is a branch of MySQL and is mainly maintained by the open source community. The purpose of using GPL to license MariaDB is to be fully compatible with MySQL, including API and the command line.

  2022-06-01 13:23:22 Views: 234
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  Summary of sql connection

  1. Inner join inner join1.1 Cross join cross joinSELECT * the Cartesian product (m *) of table A (m column), table B (n column), table C (l column) of table A (m column)

  2022-06-01 13:23:06 Views: 267