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Delete Query
MySQL Tutorial
This SQL tutorial is structured for beginners to guide them from the foundational concepts to advanced data manipulation and querying techniques in SQL. By the end of this tutorial, you will have developed a robust understanding of SQL, equipping you with the knowledge to efficiently manage and analyze data across various database systems. This guide sets the stage for your growth into a skilled data professional, ready to tackle complex data challenges and contribute to the field of data analysis and database management.
DELETE Statement
MySQL DELETE Statement
The DELETE statement from MySQL is used to delete records from a MySQL table. To remove specific records, you need to use WHERE clause along with it. If you need to define common table expressions accessible with the delete you can use the WITH clause.
Syntax
Following is the syntax of the DELETE statement
DELETE FROM table_name [WHERE Clause]Example
Assume we have created a table in MySQL with name EMPLOYEES as
CREATE TABLE EMPLOYEE( FIRST_NAME CHAR(20) NOT NULL, LAST_NAME CHAR(20), AGE INT, SEX CHAR(1), INCOME FLOAT);And if we have inserted 4 records in to it using INSERT statements as
INSERT INTO EMPLOYEE VALUES('Krishna', 'Sharma', 19, 'M', 2000),('Raj', 'Kandukuri', 20, 'M', 7000),('Ramya', 'Ramapriya', 25, 'F', 5000),('Mac', 'Mohan', 26, 'M', 2000);Following MySQL statement deletes the record of the employee with FIRST_NAME "Mac".
DELETE FROM EMPLOYEE WHERE FIRST_NAME = 'Mac';Verification
If you retrieve the contents of the table, you can see only 3 records since we have deleted one.
select * from EMPLOYEE;Output
The above query produces the following output
If you execute the DELETE statement without the WHERE clause all the records from the specified table will be deleted.
DELETE FROM EMPLOYEE;Verification
If you retrieve the contents of the table, you will get an empty set as shown below
select * from EMPLOYEE;Empty set (0.00 sec)Using where clause
Assume we have created a table with name Sales in MySQL database using CREATE TABLE statement as shown below
CREATE TABLE sales( ID INT, ProductName VARCHAR(255), CustomerName VARCHAR(255), DispatchDate date, DeliveryTime time, Price INT, Location VARCHAR(255));Following query inserts a row in the above created table
INSERT INTO SALES values(1, 'Key-Board', 'Raja', DATE('2019-09-01'), TIME('11:00:00'), 7000, 'Hyderabad'),(2, 'Earphones', 'Roja', DATE('2019-05-01'), TIME('11:00:00'), 2000, 'Vishakhapatnam'),(3, 'Mouse', 'Puja', DATE('2019-03-01'), TIME('10:59:59'), 3000, 'Vijayawada'),(4, 'Mobile', 'Vanaja', DATE('2019-03-01'), TIME('10:10:52'), 9000, 'Chennai'),(5, 'Headset', 'Jalaja', DATE('2019-04-06'), TIME('11:08:59'), 6000, 'Goa');Following query deletes the records of the Sales table with the price value greater than 6000, using the SELECT statement
DELETE FROM SALES WHERE PRICE>6000;Verification
You can verify the contents of this table after deletion using the SELECT statement as shown below
select * from sales;Output
Following is the output of the above query
Using the Order by clause
You can also use the ORDER BY clause along with the DELETE statement. If you do so, the rows in the table are deleted in the specified order.
DELETE FROM SALES WHERE PRICE > 2000 ORDER BY DeliveryTime LIMIT 2;You can verify the contents of this table after deletion using the SELECT statement as shown below
SELECT * FROM SALES;Output
The above mysql query will generate the following output
Multi-table deletes
You can delete records from more than one table using the DELETE statement. For this you need to specify the names of the tables in the statement.
Example
Suppose we have created a table with name EMPLOYEE using the following CREATE statement
CREATE TABLE EMPLOYEE( ID INT NOT NULL, FIRST_NAME CHAR(20) NOT NULL, LAST_NAME CHAR(20), AGE INT, SEX CHAR(1), INCOME FLOAT, CONTACT INT);Now, let us insert two records into the EMPLOYEE table
INSERT INTO Employee VALUES(101, 'Ramya', 'Rama Priya', 27, 'F', 9000, 101),(102, 'Vinay', 'Bhattacharya', 20, 'M', 6000, 102);Let us create another table and populated it as
CREATE TABLE CONTACT( ID INT NOT NULL, EMAIL CHAR(20) NOT NULL, PHONE LONG, CITY CHAR(20));Now, let us insert some records into the CONTACT table
INSERT INTO CONTACT (ID, EMAIL, CITY) VALUES(101, 'ramya@mymail.com', 'Hyderabad'),(102, 'vinay@mymail.com', 'Vishakhapatnam');Following query deletes records from the above created tables
DELETE EMPLOYEE, CONTACT FROM EMPLOYEE INNER JOIN CONTACT ON CONTACT.id = EMPLOYEE.id WHERE EMPLOYEE.INCOME<7000;Verification
If you verify the contents of these tables you can find the record with id value 102 (INCAME value less than 7000) is removed from the two tables
SELECT * FROM CONTACT;Following is the output of the above query
Now, let's verify the contents of the EMPLOYEE table:
SELECT * FROM EMPLOYEE;Output
The above mysql query will generate the following output