SQL WHERE Clause

The WHERE clause is a search filter that returns only true records. The WHERE clause chooses the selected records based on the given conditions. The WHERE clause is used with the queries to filter the data from billions or trillions of records. This clause is an optional part of a SELECT query, the DELETE query, and the UPDATE query.

For example, you have thousands of records on the college record track from college, and you want a final year students list of computer department, then you will use a search bar to list out computer department final year students. In the same way, the database uses the WHERE clause to search the records from the tables.

The WHERE clause syntax with the SELECT statement is as follows:

SELECT * FROM Table_Name WHERE conditions;

The Where clause in the SELECT statement is used to fetch the records from the table, but if you want to change specific records or eliminate the specific records from the table, you can use the WHERE clause in the UPDATE statement and DELETE statement.

The WHERE clause syntax with the UPDATE statement is as follows:

UPDATE Table_Name SET Column_Name = values WHERE conditions;

The WHERE clause syntax with the DELETE statement is as follows:

DELETE FROM Table_Name WHERE conditions;  

Let’s understand the SQL WHERE Clause with the help of examples.

Assume the following table, which has certain data.

Table Name: D_Students

Student_Id	Student_Name	First_ Semester	Second_ Semester	Third_ Semester	Fourth_ Semester	Fifth_ Semester	Sixth_ Semester	Total	Department_ Id
202111	Vaishnavi Patil	94	91	88	85	95	92	91	6
202112	Vaibhav Lokhande	85	90	92	80	85	82	86	2
202113	Yash Dhull	90	88	94	87	85	90	89	3
202114	Sonali Patole	95	90	92	88	92	90	91	4
202115	Axar Patel	85	80	82	86	92	84	85	1
202116	Meena Mishra	78	75	80	74	85	77	78	3
202117	Mahesh Kumbhar	75	80	75	78	80	76	77	5
202118	Sakshi Patil	80	78	74	78	80	77	78	2
202119	Sopan Bhore	70	68	75	75	80	80	75	2
202220	Prajwal Lokhande	80	85	85	75	78	80	81	4
202221	Anuja Wanare	85	88	86	82	84	85	85	7
202222	Venkatesh Iyer	90	89	87	90	92	91	90	3
202223	Anushka Sen	70	75	71	74	80	78	75	1
202224	Aakash Jain	80	75	72	74	85	80	78	7
202225	Akshay Agarwal	85	80	78	88	90	82	84	7
202226	Shwetali Bhagwat	90	80	85	88	90	80	86	6
202227	Mayuri Wagh	80	80	85	80	82	85	82	4
202228	Utkarsh Rokade	85	80	80	90	84	84	84	5
202229	Manthan Koli	85	75	84	78	82	80	81	2
202230	Mayur Jain	80	88	87	90	92	90	88	1

Example 1: Write a query to fetch student information from the D_Students table where the First_Semester percentage is 85:

SELECT * FROM D_Students WHERE First_Semester = 85;

In the above WHERE clause example, we have displayed the student's information from the table whose first_semester percentage is 85.

The following output is as follows:

Student_Id	Student_Name	First_ Semester	Second_ Semester	Third_ Semester	Fourth_ Semester	Fifth_ Semester	Sixth_ Semester	Total	Department_ Id
202112	Vaibhav Lokhande	85	90	92	80	85	82	86	2
202115	Axar Patel	85	80	82	86	92	84	85	1
202221	Anuja Wanare	85	88	86	82	84	85	85	7
202225	Akshay Agarwal	85	80	78	88	90	82	84	7
202228	Utkarsh Rokade	85	80	80	90	84	84	84	5
202229	Manthan Koli	85	75	84	78	82	80	81	2

Example 2: Write a query to fetch student information from the D_Students table where First_Semester percentage is 85 or Sixth_Semester percentage is greater than 80:

SELECT * FROM D_Students WHERE First_Semester = 85 OR Sixth_Semester > 80;

In the above WHERE clause example, we have displayed the student's information from the table whose first_semester percentage is 85 or sixth_semester percentage is greater than 80.

The following output is as follows:

Student_Id	Student_Name	First_ Semester	Second_ Semester	Third_ Semester	Fourth_ Semester	Fifth_ Semester	Sixth_ Semester	Total	Department_ Id
202111	Vaishnavi Patil	94	91	88	85	95	92	91	6
202112	Vaibhav Lokhande	85	90	92	80	85	82	86	2
202113	Yash Dhull	90	88	94	87	85	90	89	3
202114	Sonali Patole	95	90	92	88	92	90	91	4
202115	Axar Patel	85	80	82	86	92	84	85	1
202221	Anuja Wanare	85	88	86	82	84	85	85	7
202222	Venkatesh Iyer	90	89	87	90	92	91	90	3
202225	Akshay Agarwal	85	80	78	88	90	82	84	7
202227	Mayuri Wagh	80	80	85	80	82	85	82	4
202228	Utkarsh Rokade	85	80	80	90	84	84	84	5
202229	Manthan Koli	85	75	84	78	82	80	81	2
202230	Mayur Jain	80	88	87	90	92	90	88	1

Example 3: Write a query to modify the student’s information from the D_Students table where the student total percentage is less than 85.

UPDATE D_Students SET Total = Total + 5 WHERE Total < 85;

In the above WHERE clause example, we have modified the student’s information from the table whose total percentage is less than 85.

We will verify whether the record is successfully modified or not by executing the below query:

SELECT * FROM D_Students;

The following output is as follows:

Student_Id	Student_Name	First_ Semester	Second_ Semester	Third_ Semester	Fourth_ Semester	Fifth_ Semester	Sixth_ Semester	Total	Department_ Id
202111	Vaishnavi Patil	94	91	88	85	95	92	91	6
202112	Vaibhav Lokhande	85	90	92	80	85	82	86	2
202113	Yash Dhull	90	88	94	87	85	90	89	3
202114	Sonali Patole	95	90	92	88	92	90	91	4
202115	Axar Patel	85	80	82	86	92	84	85	1
202116	Meena Mishra	78	75	80	74	85	77	83	3
202117	Mahesh Kumbhar	75	80	75	78	80	76	82	5
202118	Sakshi Patil	80	78	74	78	80	77	83	2
202119	Sopan Bhore	70	68	75	75	80	80	80	2
202220	Prajwal Lokhande	80	85	85	75	78	80	86	4
202221	Anuja Wanare	85	88	86	82	84	85	85	7
202222	Venkatesh Iyer	90	89	87	90	92	91	90	3
202223	Anushka Sen	70	75	71	74	80	78	80	1
202224	Aakash Jain	80	75	72	74	85	80	83	7
202225	Akshay Agarwal	85	80	78	88	90	82	89	7
202226	Shwetali Bhagwat	90	80	85	88	90	80	86	6
202227	Mayuri Wagh	80	80	85	80	82	85	87	4
202228	Utkarsh Rokade	85	80	80	90	84	84	89	5
202229	Manthan Koli	85	75	84	78	82	80	86	2
202230	Mayur Jain	80	88	87	90	92	90	88	1

Example 4: Write a query to modify the student's information from the D_Students table where the student Second_Semester percentage is 80.

UPDATE D_Students SET Second_Semester = 83 WHERE Second_Semester = 80;

In the above WHERE clause example, we have modified the student’s information from the table whose second_semester percentage is 80.

We will verify whether the record is successfully modified or not by executing the below query:

SELECT * FROM D_Students;

The following output is as follows:

Student_Id	Student_Name	First_ Semester	Second_ Semester	Third_ Semester	Fourth_ Semester	Fifth_ Semester	Sixth_ Semester	Total	Department_ Id
202111	Vaishnavi Patil	94	91	88	85	95	92	91	6
202112	Vaibhav Lokhande	85	90	92	80	85	82	86	2
202113	Yash Dhull	90	88	94	87	85	90	89	3
202114	Sonali Patole	95	90	92	88	92	90	91	4
202115	Axar Patel	85	83	82	86	92	84	85	1
202116	Meena Mishra	78	75	80	74	85	77	83	3
202117	Mahesh Kumbhar	75	83	75	78	80	76	82	5
202118	Sakshi Patil	80	78	74	78	80	77	83	2
202119	Sopan Bhore	70	68	75	75	80	80	80	2
202220	Prajwal Lokhande	80	85	85	75	78	80	86	4
202221	Anuja Wanare	85	88	86	82	84	85	85	7
202222	Venkatesh Iyer	90	89	87	90	92	91	90	3
202223	Anushka Sen	70	75	71	74	80	78	80	1
202224	Aakash Jain	80	75	72	74	85	80	83	7
202225	Akshay Agarwal	85	83	78	88	90	82	89	7
202226	Shwetali Bhagwat	90	83	85	88	90	80	86	6
202227	Mayuri Wagh	80	83	85	80	82	85	87	4
202228	Utkarsh Rokade	85	83	80	90	84	84	89	5
202229	Manthan Koli	85	75	84	78	82	80	86	2
202230	Mayur Jain	80	88	87	90	92	90	88	1

Example 5: Write a query to remove the student's information from the D_Students table where the student Second_Semester percentage is 83.

DELETE FROM D_Students WHERE Second_Semester = 83;

In the above WHERE clause example, we have deleted the student’s information from the table whose second_semester percentage is 83.

We will verify whether the record is successfully removed or not by executing the below query:

SELECT * FROM D_Students;

The following output is as follows:

Student_Id	Student_Name	First_ Semester	Second_ Semester	Third_ Semester	Fourth_ Semester	Fifth_ Semester	Sixth_ Semester	Total	Department_ Id
202111	Vaishnavi Patil	94	91	88	85	95	92	91	6
202112	Vaibhav Lokhande	85	90	92	80	85	82	86	2
202113	Yash Dhull	90	88	94	87	85	90	89	3
202114	Sonali Patole	95	90	92	88	92	90	91	4
202116	Meena Mishra	78	75	80	74	85	77	83	3
202118	Sakshi Patil	80	78	74	78	80	77	83	2
202119	Sopan Bhore	70	68	75	75	80	80	80	2
202220	Prajwal Lokhande	80	85	85	75	78	80	86	4
202221	Anuja Wanare	85	88	86	82	84	85	85	7
202222	Venkatesh Iyer	90	89	87	90	92	91	90	3
202223	Anushka Sen	70	75	71	74	80	78	80	1
202224	Aakash Jain	80	75	72	74	85	80	83	7
202229	Manthan Koli	85	75	84	78	82	80	86	2
202230	Mayur Jain	80	88	87	90	92	90	88	1

Example 6: Write a query to remove the student's information from the D_Students table where the student department id is 2.

DELETE FROM D_Students WHERE Department_Id = 2;

In the above WHERE clause example, we have deleted the student’s information from the table whose department id is 2.

We will verify whether the record is successfully removed or not by executing the below query:

SELECT * FROM D_Students;

The following output is as follows:

Student_Id	Student_Name	First_ Semester	Second_ Semester	Third_ Semester	Fourth_ Semester	Fifth_ Semester	Sixth_ Semester	Total	Department_ Id
202111	Vaishnavi Patil	94	91	88	85	95	92	91	6
202113	Yash Dhull	90	88	94	87	85	90	89	3
202114	Sonali Patole	95	90	92	88	92	90	91	4
202116	Meena Mishra	78	75	80	74	85	77	83	3
202220	Prajwal Lokhande	80	85	85	75	78	80	86	4
202221	Anuja Wanare	85	88	86	82	84	85	85	7
202222	Venkatesh Iyer	90	89	87	90	92	91	90	3
202223	Anushka Sen	70	75	71	74	80	78	80	1
202224	Aakash Jain	80	75	72	74	85	80	83	7
202230	Mayur Jain	80	88	87	90	92	90	88	1