You can use COALESCE() function for this. In the COALESCE() function, it returns the first NON NULL value from the column. To understand the concept, let us first create a demo table
mysql> create table combineTwoColumnsDemo -> ( -> UserId int, -> UserName varchar(20), -> UserAge int -> ); Query OK, 0 rows affected (1.12 sec)
Insert some records in the table using insert command. The query is as follows −
mysql> insert into combineTwoColumnsDemo values(101,'John',23); Query OK, 1 row affected (0.16 sec) mysql> insert into combineTwoColumnsDemo values(102,'Carol',20); Query OK, 1 row affected (0.14 sec) mysql> insert into combineTwoColumnsDemo values(103,'Bob',25); Query OK, 1 row affected (0.13 sec) mysql> insert into combineTwoColumnsDemo values(104,'Mike',26); Query OK, 1 row affected (0.18 sec) mysql> insert into combineTwoColumnsDemo values(105,NULL,23); Query OK, 1 row affected (0.22 sec) mysql> insert into combineTwoColumnsDemo values(105,'Maxwell',NULL); Query OK, 1 row affected (0.15 sec)
Now you can display all records from the table using select statement. The query is as follows −
mysql> select *from combineTwoColumnsDemo;
The following is the output
+--------+----------+---------+ | UserId | UserName | UserAge | +--------+----------+---------+ | 101 | John | 23 | | 102 | Carol | 20 | | 103 | Bob | 25 | | 104 | Mike | 26 | | 105 | NULL | 23 | | 105 | Maxwell | NULL | +--------+----------+---------+ 6 rows in set (0.00 sec)
Here is the query to combine two columns in a single column
mysql> SELECT UserName, -> UserAge, -> COALESCE(UserName, UserAge) AS Combine_UserName_UserAge -> FROM combineTwoColumnsDemo;
The following is the output
+----------+---------+--------------------------+ | UserName | UserAge | Combine_UserName_UserAge | +----------+---------+--------------------------+ | John | 23 | John | | Carol | 20 | Carol | | Bob | 25 | Bob | | Mike | 26 | Mike | | NULL | 23 | 23 | | Maxwell | NULL | Maxwell | +----------+---------+--------------------------+ 6 rows in set (0.00 sec)