Overview of commonly used SQL languages (DDL, DML, DQL)

As we all know, SQL (Structure Query Language) is the core language of the database, recently learning the database, some of the basic concepts are a little ambiguous, today simply record these commonly used SQL concepts to make a distinction.

Classification:

DDL: data definition language (CREATE, DROP, ALTER)

DML: data manipulation language (INSERT, DELETE, UPDATE)

DCL: data control language (GRANT, REVOKE)

DQL: data query language (SELECT)

Overview:

1. DDL (Data Definition Language): data definition language

DDL mainly includes: CREATE, DROP, ALTER, mainly used to create a variety of objects in the database: tables, views, indexes, synonyms and so on.

Such as CREATE TABLE, CREATE VIEW, DROP TABLE and so on.

2. DML (Data Manipulation Language): data manipulation language

DML includes the addition, deletion and modification of the data in the table: INSERT, DELETE and UPDATE,DML languages mainly operate on the data in the database and affect the specific data records.

3. DCL (Data Control Language): data control language

When it comes to control, it is naturally inseparable from permissions, so the main functions of DCL language are to grant (GRANT) and reclaim (REVOKE) permissions.

4. DQL (Data Query Language): data query language

DQL, also known as "data retrieval statement", extracts the needed information from the data, and SELECT is used most frequently.

Command format: SELECT FROM WHERE