Prevent zero values in MySQL fields?

Use the BEFORE INSERT trigger on the table to prevent zero values from appearing in MySQL fields. Let us first create a table -

mysql> create table DemoTable(Value int); Query OK, 0 rows affected (0.85 sec)

Let us create a trigger to prevent zero values from appearing in a MySQL field -

mysql> DELIMITER // mysql> create trigger preventing_to_insert_zero_value before insert on DemoTable for each row begin if(new.Value = 0) then SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'You can not provide 0 value'; END if; end // Query OK, 0 rows affected (0.34 sec) mysql> DELIMITER ;

Let us insert a 0 value in the table and check if the value will is inserted. It will not allow -

mysql> insert into DemoTable values(0); ERROR 1644 (45000): You cannot provide 0 value

So, in the above table, 0 values cannot be inserted due to triggers. However, you can insert some other values.

Now let us insert some records in the table using insert command-

mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(-1000); Query OK, 1 row affected (0.41 sec)

Display all the records in the table using select statement-

mysql> select *from DemoTable;

This will produce the following output-

+-------+ | Value | +-------+ | 10 | | -1000 | +-------+ 2 rows in set (0.00 sec)

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