To avoid any issues while running a query, use IFNULL(). Let us first create a table −
mysql> create table DemoTable1793 ( StudentFirstName varchar(20), StudentLastName varchar(20) ); Query OK, 0 rows affected (0.00 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable1793 values('John','Smith'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1793 values('Carol',NULL); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1793 values(NULL,'Brown'); Query OK, 1 row affected (0.00 sec)
Display all records from the table using select statement −
mysql> select * from DemoTable1793;
This will produce the following output −
+------------------+-----------------+ | StudentFirstName | StudentLastName | +------------------+-----------------+ | John | Smith | | Carol | NULL | | NULL | Brown | +------------------+-----------------+ 3 rows in set (0.00 sec)
Here is the query to concatenate two columns when one of such column values is null −
mysql> select concat(ifnull(StudentFirstName,''),ifnull(StudentLastName,'')) from DemoTable1793;
This will produce the following output −
+----------------------------------------------------------------+ | concat(ifnull(StudentFirstName,''),ifnull(StudentLastName,'')) | +----------------------------------------------------------------+ | JohnSmith | | Carol | | Brown | +----------------------------------------------------------------+ 3 rows in set (0.00 sec)