2. Integer data type Integer data type is one of the most commonly used data types. The INT(INTEGER)INT (or INTEGER) data type is stored from -2 to 3 1 power (-2,147,483,648) to 3 1 power-1 power (2,1power).
3. The data control functions DCL(DataControlLanguage)GRANT, REVOKE, COMMIT and ROLLBACK are mainly aimed at the above operations, that is, the operations on database security and integrity, which can be simply understood as permission control.
4.SQL data definition function: you can define the three-level schema structure of the database, namely external schema, global schema and internal schema structure. In SQL, the external Schema is called View, and the global schema is abbreviated as schema. The internal mode is automatically realized by the system according to the database mode, and generally does not need the user's inquiry.