下面两个 PL/pgSQL 函数与 C 语言函数讨论中的对应函数完全相同。

CREATE FUNCTION add_one (int4) RETURNS int4 AS '
    BEGIN
        RETURN $1 + 1;
    END;
' LANGUAGE 'plpgsql';
    

CREATE FUNCTION concat_text (text, text) RETURNS text AS '
    BEGIN
        RETURN $1 || $2;
    END;
' LANGUAGE 'plpgsql';
     

这又是 C 函数中那个例子在 PL/pgSQL 中的等价物。

CREATE FUNCTION c_overpaid (EMP, int4) RETURNS bool AS '
    DECLARE
        emprec ALIAS FOR $1;
        sallim ALIAS FOR $2;
    BEGIN
        IF emprec.salary ISNULL THEN
            RETURN ''f'';
        END IF;
        RETURN emprec.salary > sallim;
    END;
' LANGUAGE 'plpgsql';
     

这个触发器保证，每当表中有行被插入或更新时，当前的用户名和 时间都会被盖章到该行中。而且它还保证给出了员工的名字并且 薪水是一个正值。

CREATE TABLE emp (
    empname text,
    salary int4,
    last_date datetime,
    last_user name);

CREATE FUNCTION emp_stamp () RETURNS OPAQUE AS '
    BEGIN
        -- Check that empname and salary are given
        IF NEW.empname ISNULL THEN
            RAISE EXCEPTION ''empname cannot be NULL value'';
        END IF;
        IF NEW.salary ISNULL THEN
            RAISE EXCEPTION ''% cannot have NULL salary'', NEW.empname;
        END IF;

        -- Who works for us when she must pay for?
        IF NEW.salary < 0 THEN
            RAISE EXCEPTION ''% cannot have a negative salary'', NEW.empname;
        END IF;

        -- Remember who changed the payroll when
        NEW.last_date := ''now'';
        NEW.last_user := getpgusername();
        RETURN NEW;
    END;
' LANGUAGE 'plpgsql';

CREATE TRIGGER emp_stamp BEFORE INSERT OR UPDATE ON emp
    FOR EACH ROW EXECUTE PROCEDURE emp_stamp();