SQL - Delete Table

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The SQL DELETE TABLE command is used to delete the existing records from a table in a database. If we wish to delete only the specific number of rows from the table, we can use the WHERE clause with the DELETE query. If we omit the WHERE clause, all rows in the table will be deleted. The SQL DELETE query operates on a single table at a time.

Since SQL DELETE is a command of Data Manipulation Language, it is important to note that it does not remove the table structure but only the data contained within it. Therefore, any constraints, indexes, or triggers defined in the table will still exist after you delete data from it.

Syntax

Following is the basic syntax for using the DELETE command in SQL −

DELETE FROM table_name;

Deleting specific rows based on single condition

We can use the SQL DELETE statement to delete specific rows from a table based on a single condition using the WHERE clause.

Syntax

Following is the syntax for deleting specific rows based on single condition −

DELETE FROM table_name
WHERE condition;

Example

Assume we have creating a table named Customers, which contains the personal details of customers including their name, age, address and salary etc.

CREATE TABLE CUSTOMERS (
   ID INT NOT NULL,
   NAME VARCHAR (20) NOT NULL,
   AGE INT NOT NULL,
   ADDRESS CHAR (25),
   SALARY DECIMAL (18, 2),       
   PRIMARY KEY (ID)
);

Now insert values into this table using the INSERT statement as follows −

INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (1, 'Ramesh', 32, 'Ahmedabad', 2000.00 );

INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (2, 'Khilan', 25, 'Delhi', 1500.00 );

INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (3, 'kaushik', 23, 'Kota', 2000.00 );

INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (4, 'Chaitali', 25, 'Mumbai', 6500.00 );

INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (5, 'Hardik', 27, 'Bhopal', 8500.00 );

INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (6, 'Komal', 22, 'MP', 4500.00 );

INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (7, 'Muffy', 24, 'Indore', 10000.00 );

If you retrieve the contents of the above created table using the SELECT command you will get the following output −

select * from Customers;
+----+----------+-----+-----------+----------+
| ID | NAME     | AGE | ADDRESS   | SALARY   |
+----+----------+-----+-----------+----------+
|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |
|  2 | Khilan   |  25 | Delhi     |  1500.00 |
|  3 | kaushik  |  23 | Kota      |  2000.00 |
|  4 | Chaitali |  25 | Mumbai    |  6500.00 |
|  5 | Hardik   |  27 | Bhopal    |  8500.00 |
|  6 | Komal    |  22 | MP        |  4500.00 |
|  7 | Muffy    |  24 | Indore    | 10000.00 |
+----+----------+-----+-----------+----------+

Now, we are trying to delete all the customers with the name ‘Hardik’ as shown in the query below −

DELETE FROM CUSTOMERS WHERE NAME='Hardik';

Output

We get the following result. We can observe that 1 row has been modified.

(1 row affected)

Verification

We can verify whether the changes are reflected in a table by retrieving its contents using the SELECT statement. Following is the query to display the records in the Customers table −

SELECT * FROM Customers;

The table displayed is as follows −

+----+----------+-----+-----------+---------+
| ID | NAME     | AGE | ADDRESS   | SALARY  |
+----+----------+-----+-----------+---------+
|  1 | Ramesh   |  32 | Ahmedabad | 2000.00 |
|  2 | Khilan   |  25 | Delhi     | 1500.00 |
|  3 | kaushik  |  23 | Kota      | 2000.00 |
|  4 | Chaitali |  25 | Mumbai    | 6500.00 |
|  6 | Komal    |  22 | MP        | 4500.00 |
|  7 | Muffy    |  24 | Indore    |10000.00 |
+----+----------+-----+-----------+---------+

Deleting specific rows based on multiple conditions

We can also use the DELETE statement to delete specific rows from a table based on multiple conditions using the WHERE clause. This is useful when we want to remove a subset of rows from a table that meet a certain criterion.

When using multiple conditions, we can use the comparison operators such as AND, OR, and NOT to refine our conditions. This way, only rows that satisfy the conditions will be deleted.

Syntax

Following is the basic syntax for deleting specific rows based on multiple conditions −

DELETE FROM table_name
WHERE condition1 AND condition2 AND ... conditionN;

Here, table_name is the name of the table from which we want to delete rows, and condition1 through conditionN are the conditions that must be met for the rows to be deleted. The AND operator is used to join the conditions together.

Example

In the following query we are trying to delete all the customers whose name is either ‘Komal’ or their address is ‘MP’ −

DELETE FROM CUSTOMERS WHERE NAME='Komal' OR ADDRESS='MP';

Output

We get the following result. We can observe that 1 row has been modified.

(1 row affected)

Verification

We can verify whether the changes are reflected in a table by retrieving its contents using the SELECT statement. Following is the query to display the records in the Customers table −

SELECT * FROM Customers;

The table displayed is as follows −

+----+----------+-----+-----------+---------+
| ID | NAME     | AGE | ADDRESS   | SALARY  |
+----+----------+-----+-----------+---------+
|  1 | Ramesh   |  32 | Ahmedabad | 2000.00 |
|  2 | Khilan   |  25 | Delhi     | 1500.00 |
|  3 | kaushik  |  23 | Kota      | 2000.00 |
|  4 | Chaitali |  25 | Mumbai    | 6500.00 |
|  7 | Muffy    |  24 | Indore    |10000.00 |
+----+----------+-----+-----------+---------+

Deleting all the records in a table

We can use the DELETE statement without a WHERE clause to delete all records in a table in SQL. This statement will remove all the rows from the specified table, effectively resetting the table to its original state (containing only the structure).

However, it's important to note that this operation cannot be undone, and all the data in the table will be permanently deleted.

Example

In here, we are trying to delete all the records from the ‘CUSTOMERS’ table −

DELETE FROM CUSTOMERS;

Output

Following is the result obtained by executing the above query

(5 rows affected)

Verification

We can verify whether the changes are reflected in a table by retrieving its contents using the SELECT statement. Following is the query to display the records in the CUSTOMERS table −

SELECT * FROM Customers;

The table displayed is as follows −

+----+----------+-----+-----------+----------+
| ID | NAME     | AGE | ADDRESS   | SALARY   |
+----+----------+-----+-----------+----------+