Scope of variables

For example, the following sample defines a variable named val in the DECLARE section of the <<outer>> block, and then defines another val variable in the DECLARE section of the <<inner>> block. Although the variables have the same name, these variables are two different variables:

<<outer>>
DECLARE
    val int4;
BEGIN
    val := 5;
    <<inner>>
    DECLARE
        val int4;
    BEGIN
        val := 7;
        RAISE NOTICE 'inner val != outer val % %', val, outer.val;
    END;
    RAISE NOTICE 'outer val is 5 %', val;
END;

In this example, the block labels inner and outer can be used to identify a specific val variable by using its fully qualified variable name. If you create this procedure as a stored procedure and run it, you would see output similar to the following:

MYDB.SCHEMA(USER)=> call vals();
NOTICE:  inner val != outer val 7 5
NOTICE:  outer val is 5 5
VALS
------

(1 row)

When you declare variables for loop iterators, the iterator variables have their own unique scope. For example, you can use a variable named val as a loop iterator. By using the same sample procedure, this would give you three unique val variables in your procedure:

<<outer>>
DECLARE
    val int4;
BEGIN
    val := 5;
    <<inner>>
    DECLARE
        val int4;
    BEGIN
        val := 7;
        RAISE NOTICE 'inner val != outer val % %', val, outer.val;
        FOR val IN 1 .. 10 LOOP
            --Note that this is a NEW val variable for the loop.
            RAISE NOTICE 'The value of val is %', val;
        END LOOP;
        RAISE NOTICE 'inner val is still 7. Value %', inner.val;
    END;
    RAISE NOTICE 'outer val is still 5. Value %', val;
END;

The following is sample output for this stored procedure:

MYDB.SCHEMA(USER)=> call vals();
NOTICE:  inner val != outer val 7 5
NOTICE:  The value of val is 1
NOTICE:  The value of val is 2
NOTICE:  The value of val is 3
NOTICE:  The value of val is 4
NOTICE:  The value of val is 5
NOTICE:  The value of val is 6
NOTICE:  The value of val is 7
NOTICE:  The value of val is 8
NOTICE:  The value of val is 9
NOTICE:  The value of val is 10
NOTICE:  inner val is still 7. Value 7
NOTICE:  inner val is still 5. Value 5
VALS
------

(1 row)