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Classification of SQL classificationexplainData definition languageFor short, DDL(Data De "nition Language) is used to define database objects: database, table, column, etc.Data manipulation languageReferred to as DML (data management language), it is used to update the records of tables in the database.Data query languageDQL(Data Query L ...

Introduction case create table test01 ( a1 int(4) not NULL, a2 int(4) not NULL, a3 int(4) not NULL, a4 int(4) not NULL ); alter table test01 add index idx_a1_a2_a3_a4(a1,a2,a3,a4); ① explain select a1,a2,a3,a4 from test01 where a1=1 and a2=2 and a3=3 and a4=4; -- Recommended writing explain select a1,a2,a3,a4 from test01 where a4= ...

Table is the main form of data storage in database. It is composed of rows and columns, which is similar to common spreadsheet.The biggest difference between tables in MySQL and other databases is that they can use different storage engines. Storage Engine is a component used to manage, access and modify physical data in MySQL. Different storag ...

Relatively speaking, the writing is fairly complete. Basically, that's all you can use in your work. A good brain is better than a bad pen. Stored procedures, stored functions, engines, transactions, scheduled tasks, triggers, variables and so on are included. You can collect those you are interested in! 1. Connect to mysql mysql is divide ...

Author: Grey Original address: Redis learning notes 7: master-slave replication and sentinel What are the problems with single machine, single node and single instance Redis? It is easy to cause single point of failure, so how to solve it? Active / standby mode At the same time, read-write separation can be realized Each node here is ...

1, Definition of Oracle collection Set is a data type in Oracle, which stores a group of data with the same data type. 2, Composition of set Consists of subscripts and values. The types of subscripts include numeric types (integer type, pls_integer and binary_integer) and string types. The types of values are all types in the database (b ...

catalogue preface 1, MHA       1. Overview       2. Composition of MHA       3. Characteristics of MHA 2, Build MySQL MHA       1. Experimental ideas       2. Experimental environment       3. Experimental steps 3, Fault simulation   &nbs ...

1, Experimental overview lab5 is mainly used to realize the B + tree index. It mainly has the functions of query, insertion and deletion. The query is mainly based on the characteristics of B + tree. The splitting of nodes should be considered for insertion (when the node tuples are full), the redistribution of elements in nodes should be cons ...

return and job management of SaltStack Experimental environment master192.168.200.142node1192.168.200.147node2192.168.200.145 1. return of saltstack component The return component can be understood as the SaltStack system stores or returns the data returned by Minion to other programs. It supports a variety of storage methods, such as MySQL, ...

catalogue 1. Meter lock   2. Row lock   two point one   Read uncommitted 2.1.1 analog dirty reading 2.2 read submitted 2.2.1 test dirty reading problem   2.2.2 non repeatable reading   2.2.3 repeatable   2.2.4 mvcc (to be supplemented) 2.2.5 unreal reading   2.2.6 serialization (to be supplemented) ...