
SQL DELETE TABLE: Understanding DELETE, TRUNCATE, and DROP Statements
SQL DELETE TABLE
Depending on a criterion, the DELETE command in SQL is used to eliminate particular rows from a table. It will remove every row from the table if no condition is specified.
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Syntax of DELETE Statement
To remove particular rows in accordance with a condition:
DELETE FROM table_name WHERE condition;
To delete all rows from a table:
DELETE FROM table_name;
Key Points about DELETE:
- Removes specific rows if a condition is given.
- Removes every row in the absence of a condition.
- Does not free up space occupied by deleted rows.
Difference Between DELETE and TRUNCATE Statements
The functions of the DELETE
and TRUNCATE
statements differ:
DELETE Statement
- Eliminates all or a subset of a table’s rows.
- Does not release the space that removed rows have taken up.
- If used in a transaction, it can be retracted.
- The table-related triggers are activated.
TRUNCATE Statement
- Removes all rows from a table instantly.
- Frees up the space occupied by the table.
- Since it doesn’t log row deletions separately, it cannot be undone.
- Triggers do not execute.
Example: Applying TRUNCATE to a Table of “employees”
Let’s consider an employees
table:
Emp_ID | Name | City | Salary |
---|---|---|---|
101 | Rohit | Mumbai | 50000 |
102 | Sanya | Bangalore | 45000 |
103 | Arjun | Hyderabad | 52000 |
To clear this table of all data and make room, use:
TRUNCATE TABLE employees;
Difference Between DROP and TRUNCATE Statements
The DROP
statement goes beyond TRUNCATE
by removing not just the data but also the table structure itself.
DROP Statement
- Eliminates the table in its entirety, including its structure.
- Removes all relationships with other tables.
- Drops integrity constraints.
- Eliminates access privileges related to the table.
- Cannot be rolled back.
TRUNCATE Statement
- Only removes data but keeps the table structure.
- Retains table relationships and constraints.
- Does not affect access privileges.
- Cannot be rolled back.
Example: On the “employees” table, using DROP
DROP TABLE employees;
The employees table will be deleted from the database entirely as a result.
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Conclusion
For efficient database administration, it is essential to comprehend the distinctions between the DELETE, TRUNCATE, and DROP statements. Utilize:
When you need to eliminate particular rows while maintaining the table’s structure, use DELETE.
When you need to swiftly clear out all rows and make room, TRUNCATE.
When you wish to eliminate a table entirely, including its relationships and structure, use DROP.
Choose wisely based on your database requirements! For more SQL insights, stay tuned to UpdateGadh.
SQL DELETE TABLE: Understanding DELETE, TRUNCATE, and DROP Statements
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