Check whether a field is empty or null in MySQL?

NULL and empty string ‘ ’ both aren’t similar in MySQL. To check the field is empty like ‘ ’or is null, you need to use the IS NULL property or something else. You can check all the conditions with CASE statement. The syntax is as follows:

SELECT *, CASE WHEN yourColumnName =’ ‘ THEN ‘yourMessage1’ WHEN yourColumnName IS NULL THEN ‘yourMessage2’ ELSE CONCAT(yourColumnName ,' is a Name') END 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 checkFieldDemo    -> (    -> Id int NOT NULL AUTO_INCREMENT,    -> Name varchar(10),    -> PRIMARY KEY(Id)    -> ); Query OK, 0 rows affected (0.64 sec)

Insert some records in the table using insert command. The query is as follows:

mysql> insert into checkFieldDemo(Name) values(NULL); Query OK, 1 row affected (0.17 sec) mysql> insert into checkFieldDemo(Name) values('John'); Query OK, 1 row affected (0.15 sec) mysql> insert into checkFieldDemo(Name) values(NULL); Query OK, 1 row affected (0.10 sec) mysql> insert into checkFieldDemo(Name) values(''); Query OK, 1 row affected (0.51 sec) mysql> insert into checkFieldDemo(Name) values('Carol'); Query OK, 1 row affected (0.14 sec) mysql> insert into checkFieldDemo(Name) values(''); Query OK, 1 row affected (0.17 sec) mysql> insert into checkFieldDemo(Name) values(NULL); Query OK, 1 row affected (0.10 sec)

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

mysql> select *from checkFieldDemo;

The following is the output:

+----+-------+ | Id | Name | +----+-------+ | 1 | NULL | | 2 | John | | 3 | NULL | | 4 | | | 5 | Carol | | 6 | | | 7 | NULL | +----+-------+ 7 rows in set (0.00 sec)

Here is the query to check field is empty or null or something else using case statement. The query is as follows:

mysql> select *,case -> when Name='' then 'It is an empty string' -> when Name is null then 'It is a NULL value' -> else concat(Name,' is a Name') -> END as ListOfValues -> from checkFieldDemo;

The following is the output:

+----+-------+-----------------------+ | Id | Name | ListOfValues | +----+-------+-----------------------+ | 1 | NULL | It is a NULL value | | 2 | John | John is a Name | | 3 | NULL | It is a NULL value | | 4 | | It is an empty string | | 5 | Carol | Carol is a Name | | 6 | | It is an empty string | | 7 | NULL | It is a NULL value | +----+-------+-----------------------+ 7 rows in set (0.00 sec)