SQlite的：保存/註冊子查詢重複使用的

Question

比方說，我有一個產品的成本很少變動商店，所以我成立了一個成本表看起來是這樣的：

CREATE TABLE costs VALUES (
    itemid INTEGER 
    cost DOUBLE 
    date DATETIME 
    FOREIGN KEY(itemid) REFERENCES items(itemid) 
); 

如果我想當前成本的輸出，當最後更新，我可以這樣做：

SELECT items.name, cost, latestdate 
FROM items 
LEFT NATURAL JOIN (
    SELECT itemid, costs.cost, latestdate 
    FROM (
     SELECT itemid, MAX(date) as latestdate 
     FROM costs 
     GROUP BY itemid 
    ) 
    LEFT NATURAL JOIN costs 
    WHERE date = latestdate 
); 

是否有可能保存子查詢，以便該查詢可以寫成這樣：

SELECT items.name, cost, latestdate 
FROM items 
LEFT NATURAL JOIN get_current_cost(); 

或者，在 「成本 - 前 - 日期」 的局面：

SELECT items.name, cost 
FROM items 
LEFT NATURAL JOIN (
    SELECT itemid, costs.cost, latestdate 
    FROM (
     SELECT itemid, MAX(date) as latestdate 
     FROM costs 
     GROUP BY itemid 
     WHERE date < *somedate* 
    ) 
    LEFT NATURAL JOIN costs 
    WHERE date = latestdate 
); 

-- Change To 

SELECT items.name, cost 
FROM items 
LEFT NATURAL JOIN get_cost_by(*somedate*) 

Answer 1

那東西被稱爲view：

CREATE VIEW current_cost AS 
SELECT itemid, cost, MAX(date) AS latestdate 
FROM costs 
GROUP BY itemid; 

（在SQLite的，a bare column in an aggregate query works）

但是，不可能使用參數。