Tutorial: How to Use SQL and PL/PGSQL Function

PL/SQL FUNCTION

A.      SQL FUNCTION

SQL function is an collection of queries. It’s usually detailed that save into one long query and database. If want to call it, we just call it with simple select query.

Example:

I’ll teach you about simple SQL function. This SQL function is about converting degree value from fahrenheit to celcius. Because formula for convert fahrenheit to celcius is (fahrenheit-32)x5/9, so we must type like this:

After success with the code, lets try with some value. I’ll put 66 degree of fahrenheit and see the result from the program.

The result is

B.      PL/PGSQL FUNCTION

PL/PGSQL is another language for using function. It’s usuallu used for complex function that normal SQL can’t handdle.

Example:

For PL/PGSQL function, I’ll give example about convert value into word predicate.

First, we need to describe range of values

> 100 or <0	Incorrect Value
≥ 90	A
≥ 70	B
≥ 60	C
≥50	D
≥ 0	E

Now, we’ve the range. Lets typo some code

After typo code, we need to test. For this example, I’ll use value 70

And the result is

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