(2) Data manipulation language, namely SQL DML. Data operation can be divided into data query and data update.
(3) Data query language, namely SQL DQL.
(4) Data control language, namely SQL DCL, includes authorization of basic tables and views, description of integrity rules, transaction control, etc.
Structured query language is an advanced non-procedural programming language, which allows users to work on advanced data structures. It does not require users to specify the storage mode of data, nor does it require users to know the specific storage mode of data, so different database systems with completely different underlying structures can use the same structured query language as the interface for data input and management. Structured query language statements can be nested, which makes it very flexible and powerful.
Extended data:
SQL can independently complete all activities in the database life cycle, including defining relational schema, inputting data, establishing database, querying, updating, maintaining, reconstructing database and controlling database security, which provides a good environment for the development of database application systems. After the database is put into operation, the mode can be modified step by step as needed without affecting the operation of the database, so that the system has good scalability.