下面是一个 Oracle 函数：

CREATE OR REPLACE FUNCTION cs_fmt_browser_version(v_name IN varchar, v_version IN varchar)
RETURN varchar IS
BEGIN
    IF v_version IS NULL THEN
        RETURN v_name;
    END IF;
    RETURN v_name || '/' || v_version;
END;
/
SHOW ERRORS;

让我们过一遍这个函数，看看它与PL/pgSQL 的差异：

那么让我们看看这个函数移植到PostgreSQL 之后是什么样子：

CREATE OR REPLACE FUNCTION cs_fmt_browser_version(VARCHAR, VARCHAR)
RETURNS VARCHAR AS '
DECLARE
    v_name ALIAS FOR $1;
    v_version ALIAS FOR $2;
BEGIN
    IF v_version IS NULL THEN
        return v_name;
    END IF;
    RETURN v_name || ''/'' || v_version;
END;
' LANGUAGE 'plpgsql';

下面的过程从一条SELECT语句抓取行，并为了 效率把结果构建成带IF语句的一个大函数。 请特别注意游标、FOR循环的差异，以及在 PostgreSQL中转义单引号的必要性。

CREATE OR REPLACE PROCEDURE cs_update_referrer_type_proc IS
    CURSOR referrer_keys IS 
        SELECT * FROM cs_referrer_keys 
        ORDER BY try_order;

    a_output VARCHAR(4000); 
BEGIN 
    a_output := 'CREATE OR REPLACE FUNCTION cs_find_referrer_type(v_host IN VARCHAR, v_domain IN VARCHAR, 
v_url IN VARCHAR) RETURN VARCHAR IS BEGIN'; 

    FOR referrer_key IN referrer_keys LOOP 
        a_output := a_output || ' IF v_' || referrer_key.kind || ' LIKE ''' || 
referrer_key.key_string || ''' THEN RETURN ''' || referrer_key.referrer_type || 
'''; END IF;'; 
    END LOOP; 

    a_output := a_output || ' RETURN NULL; END;'; 
    EXECUTE IMMEDIATE a_output; 
END; 
/ 
show errors

下面是这个函数在PostgreSQL中最终的样子：

CREATE FUNCTION cs_update_referrer_type_proc() RETURNS INTEGER AS '
DECLARE
    referrer_keys RECORD;  -- Declare a generic record to be used in a FOR
    a_output varchar(4000);
BEGIN 
    a_output := ''CREATE FUNCTION cs_find_referrer_type(VARCHAR,VARCHAR,VARCHAR) 
                  RETURNS VARCHAR AS '''' 
                     DECLARE 
                         v_host ALIAS FOR $1; 
                         v_domain ALIAS FOR $2; 
                         v_url ALIAS FOR $3;
                     BEGIN ''; 

    -- 
    -- Notice how we scan through the results of a query in a FOR loop
    -- using the FOR <record> construct.
    --

    FOR referrer_keys IN SELECT * FROM cs_referrer_keys ORDER BY try_order LOOP
        a_output := a_output || '' IF v_'' || referrer_keys.kind || '' LIKE '''''''''' 
                 || referrer_keys.key_string || '''''''''' THEN RETURN '''''' 
                 || referrer_keys.referrer_type || ''''''; END IF;''; 
    END LOOP; 
  
    a_output := a_output || '' RETURN NULL; END; '''' LANGUAGE ''''plpgsql'''';''; 
 
    -- This works because we are not substituting any variables
    -- Otherwise it would fail. Look at PERFORM for another way to run functions
    
    EXECUTE a_output; 
END; 
' LANGUAGE 'plpgsql';

下面的 Oracle PL/SQL 过程用于解析 URL 并返回若干元素（主机、 路径和查询）。它是一个过程，因为在PL/pgSQL 中函数只能返回一个值（参见 第 23.11.3 节）。在 PostgreSQL中，绕开这个问题的一种办法是把 该过程拆成三个不同的函数：一个返回主机，一个返回路径， 另一个返回查询。

CREATE OR REPLACE PROCEDURE cs_parse_url(
    v_url IN VARCHAR,
    v_host OUT VARCHAR,  -- This will be passed back
    v_path OUT VARCHAR,  -- This one too
    v_query OUT VARCHAR) -- And this one
is
    a_pos1 INTEGER;
    a_pos2 INTEGER;
begin
    v_host := NULL;
    v_path := NULL;
    v_query := NULL;
    a_pos1 := instr(v_url, '//'); -- PostgreSQL doesn't have an instr function

    IF a_pos1 = 0 THEN
        RETURN;
    END IF;
    a_pos2 := instr(v_url, '/', a_pos1 + 2);
    IF a_pos2 = 0 THEN
        v_host := substr(v_url, a_pos1 + 2);
        v_path := '/';
        RETURN;
    END IF;

    v_host := substr(v_url, a_pos1 + 2, a_pos2 - a_pos1 - 2);
    a_pos1 := instr(v_url, '?', a_pos2 + 1);

    IF a_pos1 = 0 THEN
        v_path := substr(v_url, a_pos2);
        RETURN;
    END IF;

    v_path := substr(v_url, a_pos2, a_pos1 - a_pos2);
    v_query := substr(v_url, a_pos1 + 1);
END;
/
show errors;

下面是这个过程可以怎样为PostgreSQL 改写：

CREATE OR REPLACE FUNCTION cs_parse_url_host(VARCHAR) RETURNS VARCHAR AS ' 
DECLARE 
    v_url ALIAS FOR $1; 
    v_host VARCHAR; 
    v_path VARCHAR; 
    a_pos1 INTEGER; 
    a_pos2 INTEGER; 
    a_pos3 INTEGER; 
BEGIN 
    v_host := NULL; 
    a_pos1 := instr(v_url,''//''); 

    IF a_pos1 = 0 THEN 
        RETURN '''';  -- Return a blank
    END IF; 

    a_pos2 := instr(v_url,''/'',a_pos1 + 2); 
    IF a_pos2 = 0 THEN 
        v_host := substr(v_url, a_pos1 + 2); 
        v_path := ''/''; 
        RETURN v_host; 
    END IF; 

    v_host := substr(v_url, a_pos1 + 2, a_pos2 - a_pos1 - 2 ); 
    RETURN v_host; 
END; 
' LANGUAGE 'plpgsql';