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This article mainly explains "which types of database languages are divided into". The content of the explanation in this article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought. Let's study and learn "which types of database languages are divided into"!

Database languages are divided into four categories: 1, data query language DQL;2, data manipulation language DML;3, data definition language DDL;4, data control language DCL.

The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.

SQL language is divided into four categories: data query language DQL, data manipulation language DML, data definition language DDL, data control language DCL.

1. Data query language DQL

The basic structure of data query language DQL is composed of SELECT clause, FROM clause, WHERE.

Query block consisting of clause:

SELECT

FROM

WHERE

2. Data manipulation language DML

There are three main forms of data manipulation language DML:

1) insert: INSERT

2) Update: UPDATE

3) Delete: DELETE

3. Data definition language DDL

The data definition language DDL is used to create various objects in the database-tables, views,

Indexes, synonyms, clustering, etc.

CREATE TABLE/VIEW/INDEX/SYN/CLUSTER

Table view index synonym cluster

The DDL operation is implicitly submitted! Cannot rollback

4. Data control language DCL

Data control language DCL is used to grant or retrieve certain privileges to access the database, to control the time and effect of database manipulation transactions, to monitor the database, and so on. Such as:

1) GRANT: authorization.

2) ROLLBACK [WORK] TO [SAVEPOINT]: go back to a certain point.

Rollback-ROLLBACK

The rollback command returns the database state to the last committed state. Its format is:

SQL > ROLLBACK

3) COMMIT [WORK]: submit.

There are three types of submitted data

During database insert, delete, and modify operations, the transaction is completed only when the transaction is committed to the database. Only the person who operates the database has the right to see what is done before the transaction is committed, and others can see it only after the final commit is completed.

There are three types of submission data: explicit submission, implicit submission, and automatic submission. These three types are described below.

(1) explicit submission

A commit that is done directly with the COMMIT command is an explicit commit. Its format is:

SQL > COMMIT

(2) implicit submission

A commit that is done indirectly with the SQL command is an implicit commit. These commands are:

ALTER,AUDIT,COMMENT,CONNECT,CREATE,DISCONNECT,DROP,EXIT,GRANT,NOAUDIT,QUIT,REVOKE,RENAME .

(3) automatic submission

If AUTOCOMMIT is set to ON, the system will commit automatically after the insert, modify and delete statements are executed, which is called automatic commit. Its format is: SQL > SET AUTOCOMMIT ON; thank you for your reading, the above is the "database language is divided into which categories" of the content, after the study of this article, I believe that you have a deeper understanding of the database language into which categories of this problem, the specific use of the situation also needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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