Get the type of a variable in MySQL

Question

If I define a variable like set @a = \"1\";. How can I see that @a is a string?

Answer 1

You CAN determine the type of a variable in MySQL. Create a table by selecting your variable and then check the column type:

set @a:="1"; -- your variable

drop temporary table if exists foo;
create temporary table foo select @a; -- dirty magic
desc foo;
+-------+----------+------+-----+---------+-------+
| Field | Type     | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| @a    | longtext | YES  |     | NULL    |       |
+-------+----------+------+-----+---------+-------+

Answer 2

In MySql, you cannot identify the Datatype of the variable. But there is a way to identify only the strings and Integer by using cast :

set @a = "11";
SELECT CAST(@a AS SIGNED); // Output : 11

set @a = "text";
SELECT CAST(@a AS SIGNED); // Output : 0


set @a = "121212";
SELECT CAST(@a AS SIGNED); // Output : 121212

set @a = "Mysql is open source";
SELECT CAST(@a AS SIGNED); // Output : 0

Answer 3

You cannot determine the type of a variable in MySQL.

As an alternative, you can easily CAST() your variable in the type you desire:

@a = CAST(123 AS CHAR);

More information and examples about casting in the MySQL Manual:

11.9. Cast Functions and Operators