MySQL – IS NULL Operator
Table of content
- MySQL IS NULL Operator
- IS NULL with SELECT statement
- IS NULL with COUNT() function
- IS NULL with UPDATE statement
- IS NULL with DELETE statement
- IS NULL Operator Using Client Program
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NULL values in a MySQL table fields indicate that no (or unknown) values are present in them. These values are different from zeroes or invalid values.
In MySQL, it is not possible to check NULL values with comparison operators such as =, <, or <>. Instead, we use the IS NULL and IS NOT NULL (filtering non-null values) operators.
MySQL IS NULL Operator
The IS NULL operator in MySQL is used to check whether a value in a column is NULL. Using the IS NULL operator with a conditional clause allows us to filter records that contain NULL values in a particular column.
We can also use this operator with SELECT, UPDATE, and DELETE SQL statements.
Syntax
Following is the syntax of IS NULL in MySQL −
SELECT column_name1, column_name2, ... FROM table_name WHERE column_name IS NULL;
Example
Firstly, let us create a table named CUSTOMERS using the following query −
CREATE TABLE CUSTOMERS ( ID INT NOT NULL, NAME VARCHAR (20) NOT NULL, AGE INT, ADDRESS CHAR (25), SALARY DECIMAL (18, 2), PRIMARY KEY (ID) );
In the following query, we are using the INSERT statement to insert values to the table −
INSERT INTO CUSTOMERS VALUES (1, ''Ramesh'', 32, ''Ahmedabad'', NULL), (2, ''Khilan'', 25, ''Delhi'', 1500.00), (3, ''Kaushik'', NULL, ''Kota'', 2000.00), (4, ''Chaitali'', 25, ''Mumbai'', NULL), (5, ''Hardik'', 27, ''Bhopal'', 8500.00), (6, ''Komal'', NULL, ''Hyderabad'', 4500.00), (7, ''Muffy'', 24, ''Indore'', 10000.00);
The table is created as follows −
ID | NAME | AGE | ADDRESS | SALARY |
---|---|---|---|---|
1 | Ramesh | 32 | Ahmedabad | NULL |
2 | Khilan | 25 | Delhi | 1500.00 |
3 | Kaushik | NULL | Kota | 2000.00 |
4 | Chaitali | 25 | Mumbai | NULL |
5 | Hardik | 27 | Bhopal | 8500.00 |
6 | Komal | NULL | Hyderabad | 4500.00 |
7 | Muffy | 24 | Indore | 10000.00 |
IS NULL with SELECT statement
The MySQL IS NULL operator can be used with the SELECT statement to filter the records with NULL values.
Example
In the following query, we are going to return all the records from the CUSTOMERS table where the AGE is null.
SELECT * FROM CUSTOMERS WHERE AGE IS NULL;
Output
On executing the above query, it will generate an output as shown below −
ID | NAME | AGE | ADDRESS | SALARY |
---|---|---|---|---|
3 | Kaushik | NULL | Kota | 20000.00 |
6 | Komal | NULL | Hyderabad | 20000.00 |
IS NULL with COUNT() function
We can use the MySQL IS NULL operator with the COUNT() function to count the number of records with NULL values in a particular column.
Syntax
Following is the syntax of the IS NULL with COUNT() function in MySQL −
SELECT COUNT(column_name1, column_name2, ...) FROM table_name WHERE condition IS NULL;
Example
The following query returns the count of records have a blank field (NULL) in ADDRESS column of the CUSTOMERS table.
SELECT COUNT(*) FROM CUSTOMERS WHERE ADDRESS IS NULL;
Output
On executing the above query, it will generate an output as shown below −
COUNT(*) |
---|
2 |
IS NULL with UPDATE statement
In MySQL, we can use the IS NULL operator with the UPDATE statement to update records with NULL values in a particular column.
Syntax
Following is the syntax of the IS NULL operator with the UPDATE statement in MySQL –
UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE columnname1, columnname2, ... IS NULL;
Example
In the following query, we are updating the blank (NULL) records of the SALARY column to a value of 9000.
UPDATE CUSTOMERS SET SALARY = 9000 WHERE SALARY IS NULL;
Verification
To check whether the table has been updated or not, execute the SELECT query to display the table.
ID | NAME | AGE | ADDRESS | SALARY |
---|---|---|---|---|
1 | Ramesh | 32 | Ahmedabad | 9000.00 |
2 | Khilan | 25 | Delhi | 1500.00 |
3 | Kaushik | NULL | Kota | 2000.00 |
4 | Chaitali | 25 | Mumbai | 9000.00 |
5 | Hardik | 27 | Bhopal | 8500.00 |
6 | Komal | NULL | Hyderabad | 4500.00 |
7 | Muffy | 24 | Indore | 10000.00 |
IS NULL with DELETE statement
In MySQL, we can use the IS NULL operator with the DELETE statement to delete records with NULL values in a particular column.
Syntax
Following is the syntax of the IS NULL operator with the DELETE statement in MySQL –
DELETE FROM table_name WHERE column_name(s) IS NULL;
Example
In the following query, we are trying to delete the blank (NULL) records present in the ADDRESS column of CUSTOMERS table.
DELETE FROM CUSTOMERS WHERE AGE IS NULL;
Verification
To check whether the table has been changed or not, execute the SELECT query to display the table.
ID | NAME | AGE | ADDRESS | SALARY |
---|---|---|---|---|
1 | Ramesh | 32 | Ahmedabad | NULL |
2 | Khilan | 25 | Delhi | 1500.00 |
4 | Chaitali | 25 | Mumbai | NULL |
5 | Hardik | 27 | Bhopal | 8500.00 |
7 | Muffy | 24 | Indore | 10000.00 |
IS NULL Operator Using Client Program
In addition to executing the IS NULL Operator on a MySQL Server using SQL query, we can also execute it using a client program.
Syntax
Following are the syntaxes of the IS NULL Operator in MySQL table in various programming languages −
To execute the IS NULL Operator in MySQL through a PHP program, we need to execute the SQL query with IS NULL operator using the mysqli function named query() as −
$sql = "SELECT column_name1, column_name2, ... FROM table_name WHERE column_name IS NULL"; $mysqli->query($sql);
To execute the IS NULL Operator in MySQL through a JavaScript program, we need to execute the SQL query with IS NULL operator using the mysql2 function named query() as −
sql= " SELECT column_name1, column_name2, ...FROM table_name WHERE column_name IS NULL"; con.query(sql);
To execute the IS NULL Operator in MySQL through a Java program, we need to execute the SQL query with IS NULL operator using the function named executeQuery() provided by JDBC type 4 driver −
String sql = "SELECT column_name1, column_name2, ... FROM table_name WHERE column_name IS NULL"; statement.executeQuery(sql);
To execute the IS NULL Operator in MySQL through a Python program, we need to execute the SQL query with IS NULL operator using the function named execute() provided by MySQL Connector/Python −
is_null_query = "SELECT column_name1, column_name2, ... FROM table_name WHERE column_name IS NULL" cursorObj.execute(is_null_query);
Example
Following are the implementations of this operation in various programming languages −
$dbhost = ''localhost''; $dbuser = ''root''; $dbpass = ''password''; $dbname = ''TUTORIALS''; $mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname); if($mysqli->connect_errno ) { printf("Connect failed: %s
", $mysqli->connect_error); exit(); } //printf(''Connected successfully.
''); $sql = "SELECT * FROM CUSTOMERS WHERE AGE IS NULL"; $result = $mysqli->query($sql); if ($result->num_rows > 0) { printf("Table records: n"); while($row = $result->fetch_assoc()) { printf("Id %d, Name: %s, Age: %d, Address %s, Salary %f", $row["ID"], $row["NAME"], $row["AGE"], $row["ADDRESS"], $row["SALARY"]); printf("n"); } } else { printf(''No record found.
''); } mysqli_free_result($result); $mysqli->close();
Output
The output obtained is as follows −
Table records: Id 3, Name: kaushik, Age: 0, Address Hyderabad, Salary 2000.000000 Id 6, Name: Komal, Age: 0, Address Vishakapatnam, Salary 4500.000000
var mysql = require(''mysql2''); var con = mysql.createConnection({ host: "localhost", user: "root", password: "Nr5a0204@123" }); //Connecting to MySQL con.connect(function (err) { if (err) throw err; console.log("Connected!"); console.log("--------------------------"); //Creating a Database sql = "create database TUTORIALS" con.query(sql); //Select database sql = "USE TUTORIALS" con.query(sql); //Creating CUSTOMERS table sql = "CREATE TABLE CUSTOMERS(ID INT NOT NULL,NAME VARCHAR(20),AGE INT,ADDRESS CHAR(25),SALARY DECIMAL(18, 2),PRIMARY KEY(ID));" con.query(sql); //Inserting Records sql = "INSERT INTO CUSTOMERS(ID, NAME, AGE, ADDRESS, SALARY) VALUES(1,''Ramesh'', 32, ''Hyderabad'',NULL),(2,''Khilan'', 25, NULL, 1500.00),(3,''kaushik'', NULL, ''Hyderabad'', 2000.00),(4,''Chaital'', 25, ''Mumbai'', NULL),(5,''Hardik'', 27, ''Vishakapatnam'', 8500.00),(6, ''Komal'',NULL, ''Vishakapatnam'', 4500.00),(7, ''Muffy'',24, NULL, 10000.00);" con.query(sql); //Using IS NULL Operator sql = "SELECT * FROM CUSTOMERS WHERE AGE IS NULL;" con.query(sql, function(err, result){ if (err) throw err console.log(result) }); });
Output
The output produced is as follows −
Connected! -------------------------- [ { ID: 3, NAME: ''kaushik'', AGE: null, ADDRESS: ''Hyderabad'', SALARY: ''2000.00'' }, { ID: 6, NAME: ''Komal'', AGE: null, ADDRESS: ''Vishakapatnam'', SALARY: ''4500.00'' } ]
import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class IsNullOperator { public static void main(String[] args) { String url = "jdbc:mysql://localhost:3306/TUTORIALS"; String user = "root"; String password = "password"; ResultSet rs; try { Class.forName("com.mysql.cj.jdbc.Driver"); Connection con = DriverManager.getConnection(url, user, password); Statement st = con.createStatement(); //System.out.println("Database connected successfully...!"); String sql = " SELECT * FROM CUSTOMERS WHERE AGE IS NULL"; rs = st.executeQuery(sql); System.out.println("Table records: "); while(rs.next()) { String id = rs.getString("Id"); String name = rs.getString("Name"); String age = rs.getString("Age"); String address = rs.getString("Address"); String salary = rs.getString("Salary"); System.out.println("Id: " + id + ", Name: " + name + ", Age: " + age + ", Addresss: " + address + ", Salary: " + salary); } }catch(Exception e) { e.printStackTrace(); } } }
Output
The output obtained is as shown below −
Table records: Id: 3, Name: kaushik, Age: null, Addresss: Hyderabad, Salary: 2000.00 Id: 6, Name: Komal, Age: null, Addresss: Vishakapatnam, Salary: 4500.00
import mysql.connector #establishing the connection connection = mysql.connector.connect( host=''localhost'', user=''root'', password=''password'', database=''tut'' ) cursorObj = connection.cursor() is_null_query = f""" SELECT * FROM CUSTOMERS WHERE AGE IS NULL; """ cursorObj.execute(is_null_query) # Fetching all the rows that meet the criteria filtered_rows = cursorObj.fetchall() for row in filtered_rows: print(row) cursorObj.close() connection.close()
Output
Following is the output of the above code −
(3, ''kaushik'', None, ''Hyderabad'', Decimal(''2000.00'')) (6, ''Komal'', None, ''Vishakapatnam'', Decimal(''4500.00''))
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