Replace 0 with null in MySQL?

You can use NULLIF() from MySQL to replace 0 with NULL. The syntax is as follows −

SELECT *,NULLIF(yourColumnName,0) as anyVariableName from yourTableName;

To understand the above syntax, let us create a table. The query to create a table is as follows −

mysql> create table Replace0WithNULLDemo
   -> (
   -> Id int NOT NULL auto_increment,
   -> Name varchar(20),
   -> Marks int,
   -> PRIMARY KEY(Id)
   -> );
Query OK, 0 rows affected (0.53 sec)

Now you can insert some records in the table using insert command. The query is as follows −

mysql> insert into Replace0WithNULLDemo(Name,Marks) values('John',76);
Query OK, 1 row affected (0.16 sec)

mysql> insert into Replace0WithNULLDemo(Name,Marks) values('Carol',86);
Query OK, 1 row affected (0.20 sec)

mysql> insert into Replace0WithNULLDemo(Name,Marks) values('Sam',0);
Query OK, 1 row affected (0.17 sec)

mysql> insert into Replace0WithNULLDemo(Name,Marks) values('Mike',0);
Query OK, 1 row affected (0.16 sec)

mysql> insert into Replace0WithNULLDemo(Name,Marks) values('Larry',98);
Query OK, 1 row affected (0.19 sec)

mysql> insert into Replace0WithNULLDemo(Name,Marks) values('Bob',0);
Query OK, 1 row affected (0.17 sec)

Display records from the table using select statement. The query is as follows −

mysql> select *from Replace0WithNULLDemo;

The following is the output −

+----+-------+-------+
| Id | Name  | Marks |
+----+-------+-------+
|  1 | John  | 76    |
|  2 | Carol | 86    |
|  3 | Sam   | 0     |
|  4 | Mike  | 0     |
|  5 | Larry | 98    |
|  6 | Bob   | 0     |
+----+-------+-------+
6 rows in set (0.00 sec)

Let us now replace 0 with NULL. The query is as follows −

mysql> select *,NULLIF(Marks,0) as ReplaceZeroWithNULL from Replace0WithNULLDemo;

The following is the output displaying a new column wherein new have replaced 0 with NULL −

+----+-------+-------+---------------------+
| Id | Name  | Marks | ReplaceZeroWithNULL |
+----+-------+-------+---------------------+
| 1  | John  | 76    | 76                  |
| 2  | Carol | 86    | 86                  |
| 3  | Sam   | 0     | NULL                |
| 4  | Mike  | 0     | NULL                |
| 5  | Larry | 98    | 98                  |
| 6  | Bob   | 0     | NULL                |
+----+-------+-------+---------------------+
6 rows in set (0.00 sec)