What is Delete Query?
In SQL, the DELETE Query removes existing records from a table. Depending on the condition specified in the WHERE clause, we can delete a single record or multiple records.
NOTE: This command must be used with extreme caution because it permanently deletes the data.
DELETE FROM table_name [WHERE condition];
where table_name is the table that has to be deleted, the WHERE clause in SQL DELETE statement is optional here.
Let’s take an example of student table:
- Delete all the records:
DELETE FROM student;
The given query will delete all the records from the student table, as we haven’t mentioned any conditions for deletion.
- Delete a particular Record from a Table:
DELETE FROM student WHERE NAME="SUJIT";
The above query will delete two records from the above table as there are two students with the name “SUJIT“.
TRUNCATE vs DELETE:
TRUNCATE and DELETE are both SQL commands for removing data from a table, but they have some key differences:
- DELETE is a DML (Data Manipulation Language) operation, whereas TRUNCATE is a DDL (Data Definition Language) operation. This means that TRUNCATE is used to modify the table’s structure, whereas DELETE is used to modify the data within the table.
- TRUNCATE deletes all rows from a table, whereas DELETE deletes specific rows based on a condition.
- TRUNCATE is not transactional, which means it cannot be reversed. DELETE, on the other hand, is a transactional command that can be reversed if necessary.
- DELETE does not reset the identity value to the initial seed value, whereas TRUNCATE does.
Note: also read about SQL: UPDATE Query
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