Differences Between DELETE, DROP and TRUNCATE
Introduction
In MS SQL Server, there are three main ways to remove data from a table: DELETE, DROP, and TRUNCATE. Each method has its own advantages and disadvantages, and it’s important to choose the right method for the task at hand.
DELETE
- Delete is a DML (Data Manipulation Language) operation that is used to remove one or more rows from a table. The delete command can be used to delete specific rows based on a condition or to delete all the rows in a table. When a delete command is executed, the deleted rows are logged, and they can be rolled back if necessary.
- In other words, the DELETE statement is used to remove one or more rows from a table based on a condition. This statement can be used to remove specific rows or all rows from a table. The syntax for the DELETE statement is as follows:
DELETE FROM table_name
WHERE CONDITION;
DELETE FROM table_name
WHERE CONDITION;Example:
Consider a table called “employees” with the following data:
ID | Name | Department |
1 | Alice | Sales |
2 | Bob | HR |
3 | Charlie | Marketing |
- To delete all employees in the “Sales” department, you would use the following DELETE statement:
DELETE FROM HR.Employees
WHERE Department = 'Sales'Advantages:
- Can selectively remove specific rows based on a condition.
- Allows the use of a WHERE clause to specify which rows to remove.
Disadvantages:
- Can be slower than TRUNCATE or DROP, especially for large tables.
- Deletes can be rolled back, which can affect performance.
Drop
- Drop is a DDL operation used to remove an entire table or database from the system. The drop command deletes both the table and its data. When a drop command is executed, all the data in the table is permanently deleted, and the table is removed from the database.
- In other words, the DROP statement is used to remove an entire table from the database. This statement removes the table and all associated objects, such as triggers, constraints, and indexes. The syntax for the DROP statement is as follows:
DROP TABLE Table_Name;Example:
To drop the “employees” table, you would use the following DROP statement:
DROP TABLE HR.Employees;Advantages:
- Removes the entire table and all associated objects.
- Can be faster than DELETE for large tables.
Disadvantages:
- Cannot selectively remove specific rows or columns.
- Cannot be rolled back, which can lead to accidental data loss.
Truncate
- Truncate is a DDL (Data Definition Language) operation used to quickly remove all the rows from a table without logging the individual row deletions. The truncate command is used to delete all the data from a table, but it does not delete the table itself. It is much faster than the delete command because it doesn’t log each row deletion.
- In other words, the TRUNCATE statement is used to remove all rows from a table. This statement is faster than because it removes all rows at once, rather than one row at a time. The syntax for the TRUNCATE statement is as follows:
TRUNCATE TABLE Table_Name;Example:
TRUNCATE TABLE HR.Employees;To truncate the “employees” table, you would use the following TRUNCATE statement:
What is the main difference between Truncate, Delete, and Drop commands in MS SQL?
Truncate, delete, and drop are commonly used SQL commands used to manipulate data in a database. While they may seem similar, there are some important differences between them.
Main Differences:
- Truncate is a DDL operation, while delete is a DML operation.
- Truncate removes all rows from a table, while delete removes specific rows based on a condition.
- Truncate is much faster than delete because it does not log each row deletion.
- Drop removes the entire table from the database, while truncate and delete only remove rows from the table.
- Drop is a DDL operation, and it cannot be rolled back once executed, while truncate and delete can be rolled back.
Differentiating the Truncate, Drop, and Delete commands in MS SQL:
Table 1:
Command | Functionality | Transaction Log | Recovery |
|---|---|---|---|
Truncate | Removes all the rows from a table | Minimal logging, does not log individual row deletions | Cannot roll back |
Delete | Removes specific rows from a table | Fully logged, logs each row deletion | Can roll back |
Drop | Removes an entire table from the database | Fully logged, logs each row deletion | Cannot roll back |
- As we can see from the table, Truncate removes all the rows from a table, but it does not log individual row deletions. Delete, on the other hand, removes specific rows from a table, and it logs each row deletion. Drop removes the entire table from the database and logs each row deletion.
- Truncate is much faster than Delete because it does not log each row deletion. Delete is slower because it logs each row deletion, and the transaction log can grow quickly if many rows are being deleted.
- It is important to note that Truncate and Drop cannot be rolled back once executed, while Delete can be rolled back.
- In conclusion, the choice between Truncate, Delete, and Drop depends on the requirements of the situation. Truncate is used when you want to remove all the rows from a table quickly, Delete is used to remove specific rows, and Drop is used to remove an entire table from the database.
Table 2:
Command | Functionality | Transaction Log | Recovery | Example |
|---|---|---|---|---|
Truncate | Removes all the rows from a table | Minimal logging, does not log individual row deletions | Cannot roll back | TRUNCATE TABLE TableName; |
Delete | Removes specific rows from a table | Fully logged, logs each row deletion | Can roll back | DELETE FROM TableName WHERE Condition; |
Drop | Removes an entire table from the database | Fully logged, logs each row deletion | Cannot roll back | DROP TABLE TableName; |
Conclusion:
- Truncate, delete, and drop are SQL commands used to manipulate data in a database. They all have different functionalities and are used for different purposes. Truncate is used to quickly remove all the rows from a table without logging each row deletion, delete is used to remove specific rows from a table, and drop is used to remove the entire table from the database. It is important to understand the differences between these commands to use them correctly in different scenarios.
- Choosing the right method to remove data from a table in MS SQL Server depends on the task at hand. If you want to remove specific rows based on a condition, use DELETE. If you want to remove an entire table, use DROP. If you want to remove all rows from a table, use TRUNCATE. It’s important to consider the advantages and disadvantages of each method before making a decision. By following these guidelines, you can ensure that your data is removed safely and efficiently.
- Truncate, delete, and drop are SQL commands used to manipulate data in a database. They all have different functionalities and are used for different purposes. Truncate is used to quickly remove all the rows from a table without logging each row deletion, delete is used to remove specific rows from a table, and drop is used to remove the entire table from the database. It is important to understand the differences between these commands to use them correctly in different scenarios.
