The concept of a database dml, ddl dcl and the

Learned database will certainly know DML, DDL and DCL three languages, this conceptual basis of what is necessary to keep in mind.

DML (Data Manipulation Lanaguage, data manipulation language)

DML is that we often use SELECT, INSERT, UPDATE, and DELETE statements, primarily used for data CRUD operations.

- query 
SELECT column name FROM table name
 - insert 
INSERT  INTO table name (column 1, column 2, ...) VALUES (value 1, value 2, ....)
 - update 
UPDATE table name SET column name = The new value WHERE column name = conditional value
 - delete 
dELETE  the FROM table name WHERE column name = conditional value

DDL (Data Definition Language, Data Definition Language)

DDL is that some statements we use when creating the table, such as CREATE, ALTER, DROP and so on. DDL is mainly used in the definition or changing the structure of the table, the data type, or the links between the tables and other constraint initialization work.

- Create a table 
the CREATE  TABLE table name 
( 
    column name data type 1, 
    column 2 data type name, 
    column name 3 data type, 
    .... 
) 
- modify the table column names 
the ALTER  TABLE table name
 the ALTER  the COLUMN new column name for the new data types
 - delete a table 
DROP  tABLE table name
 - delete the database 
DROP  dATABASE database name

DCL (Data Control Language, a database control language)

DCL is used to set or change the database user or role privileges statements include GRANT, DENY, REVOKE and other statements, this level should be mainly DBA to do, but if you are a small company may still have to do, like deploying database when you do not how the line, especially in this user-driven ORACLE database.

 

"You will not suddenly appear, No. 4 in the next line."