SQL | DROP, TRUNCATE

DROP

DROP is used to delete a whole database or just a table.The DROP statement destroys the objects like an existing database, table, index, or view.
A DROP statement in SQL removes a component from a relational database management system (RDBMS).
Syntax:

DROP object object_name

Examples:
DROP TABLE table_name;
table_name: Name of the table to be deleted.

DROP DATABASE database_name;
database_name: Name of the database to be deleted.

TRUNCATE

TRUNCATE statement is a Data Definition Language (DDL) operation that is used to mark the extents of a table for deallocation (empty for reuse). The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms. It was officially introduced in the SQL:2008 standard.
The TRUNCATE TABLE mytable statement is logically (though not physically) equivalent to the DELETE FROM mytable statement (without a WHERE clause).
Syntax:

TRUNCATE TABLE  table_name;
table_name: Name of the table to be truncated.
DATABASE name - student_data

DROP vs TRUNCATE

  • Truncate is normally ultra-fast and its ideal for deleting data from a temporary table.
  • Truncate preserves the structure of the table for future use, unlike drop table where the table is deleted with its full structure.
  • Table or Database deletion using DROP statement cannot be rolled back, so it must be used wisely.

table1

table12

Queries

  • To delete the whole database
    DROP DATABASE student_data; 
    

    After running the above query whole database will be deleted.

  • To truncate Student_details table from student_data database.
    TRUNCATE TABLE Student_details;
    

    After running the above query Student_details table will be truncated, i.e, the data will be deleted but the structure will remain in the memory for further operations.

References:

  • https://en.wikipedia.org/wiki/Truncate_(SQL)
  • https://en.wikipedia.org/wiki/Data_definition_language#DROP_statement

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