SQL: Truncate, Drop, Rename Query

The various DDL commands that are used to redefine the tables will be covered in this tutorial.

Truncate Query:

TRUNCATE statement is a Data Definition Language (DDL) operation that is used to mark the extent of a table for deallocation (empty for reuse). This method instantly deletes all of the data from a table while often evading several integrity-checking techniques. It was introduced formally in the SQL:2008 standard. The DELETE FROM mytable statement and the TRUNCATE TABLE mytable statement are similar theoretically but not physically (without a WHERE clause).

Syntax:

TRUNCATE TABLE  table_name;

Example:

Student_ID	Student_Name	Student_Course	Student_Marks
1	Anuj	B.tech	88
2	Raman	MCA	98
3	Shyam	BBA	92

Query to truncate the table:

TRUNCATE TABLE  Student;

The above query will delete all the records from the table Student.

Output:

Student_ID	Student_Name	Student_Course	Student_Marks

Drop Query:

The drop command is used to completely remove a table from a database and erases the table’s structure. The drop command deletes all of the table’s indexes, constraints, triggers, and other definitional elements. When the DROP command is performed, the data kept in the database is also gone and cannot be restored.

Syntax:

DROP TABLE table_name;  

Example:

This query deletes the created Student table from the database:

DROP TABLE Student;  

Rename Query:

The RENAME command in a database can be used to rename a table. The syntax for the rename command is as follows:

RENAME TABLE old_table_name to new_table_name

Example:

Query to rename the Student table to Student_Details.

RENAME TABLE Student to Student_Details

Output:

Student_ID	Student_Name	Student_Course	Student_Marks

Note: also read about SQL: ALTER command

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