類型EXECUTE在postgresql查詢中不存在

Question

我試圖創建以下函數。功能已成功創建，但試圖調用它時的投擲錯誤

type EXECUTE does not exist!

CREATE OR REPLACE FUNCTION exa(ids text, length integer, fields text) returns text AS 
$BODY$ 
DECLARE 
    chars INT[] := string_to_array(ids, ','); 
    result text := ''; 
    i integer := 0; 
    temp text := ''; 
BEGIN 

    for i in 1..length loop 
     temp := EXECUTE 'SELECT ' || fields || ' from user_index where userid=' || chars[i]; 
      result := result || temp; 
     IF i < length THEN 
      result := result || ',';  
     END IF; 
    end loop; 
    return result; 
END 
$BODY$ language plpgsql; 

Answer 1

假設fields應該是一個列名。

CREATE OR REPLACE FUNCTION exa(ids text, length integer, fields text 
           ,OUT result text) AS 
$BODY$ 
DECLARE 
    _chars INT[] := string_to_array(ids, ','); 
    i integer := 0; 
    _temp text := ''; 
    _arr text[]; 
BEGIN 
    FOR i IN 1..length loop 
     EXECUTE 'SELECT ' || fields || ' FROM user_index WHERE userid = chars[i]' 
     INTO temp; 
     _arr := _arr || temp; 
    END LOOP; 
    result := array_to_string(result, ','); 

    RETURN; 
END 
$BODY$ language plpgsql; 

但真的只是：

CREATE OR REPLACE FUNCTION exa(ids text, fields text, OUT result text) AS 
$BODY$ 
BEGIN 
    EXECUTE 
    format($$SELECT string_agg(%I, ',') 
      FROM user_index 
      JOIN unnest(string_to_array($1, ',')::int[]) i(userid) 
                 USING (userid)$$ 
     ,fields) 
    USING ids 
    INTO result; 
END 
$BODY$ language plpgsql; 

電話：

SELECT exa('10,11,12', 'kat') 

而且一定要避免使用format()與%I或其他一些理智的方法SQL注入。嘗試搜索工具。許多類似的答案，在這裏SO - 像這樣的（有更多的解釋和鏈接）：
INSERT with dynamic table name in trigger function