What to assign to a MySQL column that must not be empty?
Define with NOT NULL, if a column must not be empty. Let us first create a table with one of the columns as NOT NULL −
mysql> create table DemoTable1895
(
Id int NOT NULL,
FirstName varchar(20),
LastName varchar(20) NOT NULL
);
Query OK, 0 rows affected (0.00 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable1895 values(100,'John','Smith');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1895 values(NULL,'Chris','Brown');
ERROR 1048 (23000): Column 'Id' cannot be null
mysql> insert into DemoTable1895 values(102,'Carol',NULL);
ERROR 1048 (23000): Column 'LastName' cannot be null
mysql> insert into DemoTable1895 values(103,NULL,'Miller');
Query OK, 1 row affected (0.00 sec)
Display all records from the table using select statement −
mysql> select * from DemoTable1895;
This will produce the following output −
+-----+-----------+----------+
| Id | FirstName | LastName |
+-----+-----------+----------+
| 100 | John | Smith |
| 103 | NULL | Miller |
+-----+-----------+----------+
2 rows in set (0.00 sec)
Published on 27-Dec-2019 06:58:48
