How can we apply COALESCE() function on data values ​​of MySQL table?

If we want to apply the COALESCE() function on the data values ​​of the MySQL table, then we need to use the column name as the parameter of the function. If there is a NULL value in the first column, it checks the next column and so on until it finds a non-NULL value. We demonstrate the above concept using data from the 'employee' table as shown below:

mysql> Select * from employee;
+----+------------+-------------+-----------+
| Id | First_Name | Middle_Name | Last_Name |
+----+------------+-------------+-----------+
| 1  | Advik      | NULL        | Jhamb     |
| 2  | Rahul      | Kumar       | Sharma    |
| 3  | Raman      | Singh       | Rajput    |
| 4  | Krishan    | Kumar       | Khurana   |
| 5  | Sachin     | Ramesh      | Tendulkar |
| 6  | NULL       | Kumar       | Gaurav    |
| 7  | NULL       | Singh       | Parmar    |
+----+------------+-------------+-----------+
7 rows in set (0.00 sec)

mysql> Select COALESCE(First_Name, Middle_Name,Last_Name)AS Name FROM Employee;
+---------+
| Name    |
+---------+
| Advik   |
| Rahul   |
| Raman   |
| Krishan |
| Sachin  |
| Kumar   |
| Singh   |
+---------+
7 rows in set (0.03 sec)

In the above example, the COALESCE() function has three parameters and the above query returns the names from First_Name, Middle_Name and Last_Name , and if First_Name is NULL, returns the value of Middle_Name. Then for Last_Name, if First_Name and Middle_Name are NULL, return the value of Last_Name. If First_Name, Middle_Name and Last_Name are all NULL, NULL is returned.

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