interval values can be written using the following verbose syntax: [@] quantity unit [quantity unit...] [direction] where quantity is a number (possibly signed); unit is microsecond, millisecond, second, minute, hour, day, week, month, year, decade, century, millennium, or abbreviations or plurals of these units

scale: 3 means 3 of those digits come after the decimal point (surely it should be the other way round, scale for how big the number is and precision for its decimal places?):

You can use the pg_typeof() function, which also works well for arbitrary values. SELECT pg_typeof("stu_id"), pg_typeof(100)

In this case it's probably better to have the function return a tabletype, RETURNS table, or define the output with OUT variables. Therecord defining syntax at time of query: SELECT foo() AS (a int, b text);

Also, In PostgreSQL, all tables already have a type created by the same name.

I personaly prefer the types approach. it assures that if the function is edited, all the queries will return correct results.

If anyone else wonders How to just get data type of a varible (not column) you can use the pg_typeof(any) function.