DDL Queries

                        DDL(DATA DEFINITION LANGUAGE)

           DDL refers to "Data Definition Language", a subset of SQL statements that change the structure of the database schema in some way, typically by creating, deleting, or modifying schema objects such as databases, tables, and views.

   ➤CREATE

➤ALTER

➤DROP

➤TRUNCATE

  ➤RENAME

➥ Create Query:-

➧    CREATE TABLE EMP(EMPID NUMBER(5),NAME VARCHAR2(15), SALARY  NUMBER(7,2),EMAIL VARCHAR(20));

➧    CREATE TABLE DEPT AS SELECT * FROM DEPARTMENTS;

"This Query will Create Table when we want to copy the data of any table into new table.Here old table is DEPARTMENTS.

➥Alter Query:- ALTER' COMMAND IS USED TO MODIFY TABLE STRUCTURE.

➧    ALTER TABLE EMP MODIFY EMPID NUMBER(10); 

"this will change the data type of any attribute in the table."

➧ ALTER TABLE EMP RENAME COLUMN NAME TO FIRST_NAME;

➧  ALTER TABLE EMP DROP COLUMN HIRE_DATE;

➥Drop Query:-DROP statement allows you to remove database, table, index or stored procedure.

➧  DROP TABLE TABLE_NAME;

➥Truncate Query:-TRUNCATE operation is used to delete all table records.

Differences between DELETE and TRUNCATE commands are:

• TRUNCATE is really faster.
• TRUNCATE cannot be rolled back.
• TRUNCATE command does not invoke ON DELETE triggers.

➧  TRUNCATE TABLE TABLE_NAME;

➥Rename Query:-RENAME command is used to rename SQL table.

➧  RENAME EMP TO E;