September 2017 Update

Task/Fibonacci-sequence/SQL/fibonacci-sequence-3.sql

@@ -1,27 +1,16 @@
-CREATE FUNCTION fib(n int) RETURNS numeric AS $$
-    -- This recursive with generates endless list of Fibonacci numbers.
-    WITH RECURSIVE fibonacci(current, previous) AS (
-        -- Initialize the current with 0, so the first value will be 0.
-        -- The previous value is set to 1, because its only goal is not
-        -- special casing the zero case, and providing 1 as the second
-        -- number in the sequence.
-        --
-        -- The numbers end with dots to make them numeric type in
-        -- Postgres. Numeric type has almost arbitrary precision
-        -- (technically just 131,072 digits, but that's good enough for
-        -- most purposes, including calculating huge Fibonacci numbers)
-        SELECT 0., 1.
-    UNION ALL
-        -- To generate Fibonacci number, we need to add together two
-        -- previous Fibonacci numbers. Current number is saved in order
-        -- to be accessed in the next iteration of recursive function.
-        SELECT previous + current, current FROM fibonacci
-    )
-    -- The user is only interested in current number, not previous.
-    SELECT current FROM fibonacci
-    -- We only need one number, so limit to 1
-    LIMIT 1
-    -- Offset the query by the requested argument to get the correct
-    -- position in the list.
-    OFFSET n
-$$ LANGUAGE SQL RETURNS NULL ON NULL INPUT IMMUTABLE;
+SQL> with fib(e,f) as (select 1, 1 from dual union all select e+f,e from fib where e <= 55) select f from fib;
+
+         F
+----------
+         1
+         1
+         2
+         3
+         5
+         8
+        13
+        21
+        34
+        55
+
+10 rows selected.