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There are two ways to assign a value to a user-defined variable. You can use either := or = as the assignment operator in the SET statement. For example, the statement assigns number 100 to the variable @counter. The second way to assign a value to a variable is to use the SELECT statement.
When a variable is first declared, its value is set to NULL. To assign a value to a variable, use the SET statement. This is the preferred method of assigning a value to a variable. A variable can also have a value assigned by being referenced in the select list of a SELECT statement.
You can store a value in a user-defined variable in one statement and refer to it later in another statement. This enables you to pass values from one statement to another. User variables are written as @ var_name , where the variable name var_name consists of alphanumeric characters, . , _ , and $ .
The SQL SELECT Statement The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set.
In a stored procedure do this:
SELECT COUNT(barcode) AS count into @myVar FROM movieitems;
SELECT @someVariable := COUNT(barcode) FROM movie ...
You can then use @someVariable in other queries.
E.g.
SELECT * FROM some_table WHERE some_field > @someVariable;
And you can also manipulate the variable using SET:
SET @someVariable = @someVariable + 1;
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