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-- SIMPLE
CREATE OR REPLACE FUNCTION omnidb.function_01(text, text)
RETURNS text AS $$
BEGIN
RETURN $1 || ' ' || $2;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_01('hello', 'world');
-- --> 'hello world'
---
-- PARAMETER ALIAS
CREATE OR REPLACE FUNCTION omnidb.function_02(int, int)
RETURNS int AS $$
DECLARE
i ALIAS FOR $1;
j ALIAS FOR $2;
sum int;
BEGIN
sum := i + j;
RETURN sum;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_02(41, 1);
-- --> 42
---
-- NAMED PARAMETERS
CREATE OR REPLACE FUNCTION omnidb.function_03(i int, j int)
RETURNS int AS $$
DECLARE
sum int;
BEGIN
sum := i + j;
RETURN sum;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_03(41, 1);
-- --> 42
---
-- CONTROL STRUCTURES: IF
CREATE OR REPLACE FUNCTION omnidb.function_04(i int)
RETURNS boolean AS $$
DECLARE
tmp int;
BEGIN
tmp := i % 2;
IF tmp = 0 THEN
RETURN true;
ELSE
RETURN false;
END IF;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_04(3);
-- --> f
-- SELECT omnidb.function_04(32);
-- --> t
---
-- CONTROL STRUCTURES: FOR ... LOOP
CREATE OR REPLACE FUNCTION omnidb.function_05(i numeric)
RETURNS numeric AS $$
DECLARE
tmp numeric; result numeric;
BEGIN
result := 1;
FOR tmp IN 1 .. i LOOP
result := result * tmp;
END LOOP;
RETURN result;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_05(42::numeric);
-- --> 1405006117752879898543142606244511569936384000000000
---
-- CONTROL STRUCTURES: WHILE ... LOOP
CREATE OR REPLACE FUNCTION omnidb.function_06(i numeric)
RETURNS numeric AS $$
DECLARE tmp numeric; result numeric;
BEGIN
result := 1; tmp := 1;
WHILE tmp <= i LOOP
result := result * tmp;
tmp := tmp + 1;
END LOOP;
RETURN result;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_06(42::numeric);
-- --> 1405006117752879898543142606244511569936384000000000
---
-- RECURSIVE
CREATE OR REPLACE FUNCTION omnidb.function_07(i numeric)
RETURNS numeric AS $$
BEGIN
IF i = 0 THEN
RETURN 1;
ELSIF i = 1 THEN
RETURN 1;
ELSE
RETURN i * omnidb.function_07(i - 1);
END IF;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_07(42::numeric);
-- --> 1405006117752879898543142606244511569936384000000000
---
-- RECORD TYPES
CREATE OR REPLACE FUNCTION omnidb.function_08()
RETURNS text AS $$
DECLARE
tmp RECORD;
BEGIN
SELECT INTO tmp 1 + 1 AS a, 2 + 2 AS b;
RETURN 'a = ' || tmp.a || '; b = ' || tmp.b;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_08();
-- --> 'a = 2; b = 4'
---
-- PERFORM
CREATE TABLE omnidb.foo(x integer);
CREATE OR REPLACE FUNCTION omnidb.function_09_aux() RETURNS void AS
$$ INSERT INTO omnidb.foo VALUES (41),(42) $$ LANGUAGE sql;
CREATE OR REPLACE FUNCTION omnidb.function_09()
RETURNS text AS $$
BEGIN
PERFORM omnidb.function_09_aux();
RETURN 'OK';
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_09();
-- --> 'OK'
-- SELECT * FROM omnidb.foo;
-- --> 41, 42
---
-- DYNAMIC SQL
CREATE OR REPLACE FUNCTION omnidb.function_10(i int)
RETURNS omnidb.foo AS $$
DECLARE
rec RECORD;
BEGIN
EXECUTE 'SELECT * FROM omnidb.foo WHERE x = ' || i INTO rec;
RETURN rec;
END;
$$ LANGUAGE plpgsql;
-- SELECT * FROM omnidb.function_10(42);
-- --> 42
---
-- CURSORS
CREATE OR REPLACE FUNCTION omnidb.function_11()
RETURNS numeric AS $$
DECLARE
tmp RECORD; result numeric;
BEGIN
result := 0.00;
FOR tmp IN SELECT * FROM omnidb.foo LOOP
result := result + tmp.x;
END LOOP;
RETURN result;
END;
$$ LANGUAGE plpgsql;
-- SELECT omnidb.function_11();
-- --> 83
---
-- ALTERNATIVE FUNCTION TERMINATOR
CREATE FUNCTION omnidb.function_12(text)
RETURNS text
AS 'DECLARE
str text;
ret text;
i integer;
len integer;
BEGIN
str := upper($1);
ret := '''';
i := 1;
len := length(str);
WHILE i <= len LOOP
ret := ret || substr(str, i, 1) || '' '';
i := i + 1;
END LOOP;
RETURN ret;
END;'
LANGUAGE 'plpgsql';
-- SELECT omnidb.function_12('Hello World');
-- --> 'H E L L O W O R L D'
---
-- ERROR HANDLING
CREATE OR REPLACE FUNCTION omnidb.function_13(a integer, b integer)
RETURNS integer AS $$
BEGIN
RETURN a + b;
EXCEPTION
WHEN numeric_value_out_of_range THEN
-- do some important stuff
RETURN -1;
WHEN OTHERS THEN
-- do some other important stuff
RETURN -1;
END;
$$ LANGUAGE plpgsql;
---
-- NESTED EXCEPTION BLOCKS
CREATE TABLE omnidb.bar(a integer, b text);
CREATE FUNCTION omnidb.function_14(key integer, data text)
RETURNS void AS $$
BEGIN
LOOP
UPDATE omnidb.bar SET b = data WHERE a = key;
IF found THEN RETURN;
END IF;
BEGIN
INSERT INTO omnidb.bar (a, b) VALUES (key, data);
RETURN;
EXCEPTION WHEN unique_violation THEN
-- do nothing
END;
END LOOP;
EXCEPTION WHEN OTHERS THEN
-- do something else
END;
$$ LANGUAGE plpgsql;
|
