選擇postgreSQL中最準確的數據？

Question

我在我的數據庫中有地址和定價數據。定價數據不完整，通常適用於某個地區，其他時間適用於特定地址。我有一個plpgsql函數可以檢索最準確的價格數據。我目前在我的功能中有：

SELECT price_est.sau_price_avg INTO _est_price FROM price_est WHERE price_est.neighbourhood_id = _neighbourhood_id AND --neighbourhood level 
                    price_est.district_id = _district_id AND 
                    price_est.municipality_id = _municipality_id AND 
                    price_est.county_id = _county_id; 
IF _est_price IS NULL THEN 
    SELECT price_est.sau_price_avg INTO _est_price FROM price_est WHERE price_est.neighbourhood_id IS NULL AND   --district level 
                     price_est.district_id = _district_id AND 
                     price_est.municipality_id = _municipality_id AND 
                     price_est.county_id = _county_id; 
END IF; 
... 

如果數據在某處不可用，那麼沒有對該區域的外鍵引用。

這對我來說似乎是一個非常笨拙的解決方案。有一個更好的方法嗎？

我可以對錶格進行更改，並且數據表示是必要的。

-----------------------------------編輯---------- -------------------------

我做了尼克巴恩斯的回答爲我工作是這樣的：

SELECT price_est.sau_price_avg 
FROM price_est 
WHERE 
    (price_est.county_id = _county_id OR price_est.county_id IS NULL) AND 
    (price_est.municipality_id = _municipality_id OR price_est.municipality_id IS NULL) AND 
    (price_est.district_id = _district_id OR price_est.district_id IS NULL) AND 
    (price_est.neighbourhood_id = _neighbourhood_id OR price_est.neighbourhood_id IS NULL) 
ORDER BY price_est.neighbourhood_id NULLS LAST, 
     price_est.district_id NULLS LAST, 
     price_est.municipality_id NULLS LAST, 
     price_est.county_id NULLS LAST 
LIMIT 1; 

Answer 1

你可以在同一時間選擇他們兩個，並使用ORDER BY/LIMIT精度的順序優先：

SELECT price_est.sau_price_avg 
INTO _est_price 
FROM price_est 
WHERE 
    (price_est.neighbourhood_id = _neighbourhood_id OR price_est.neighbourhood_id IS NULL) AND 
    price_est.district_id = _district_id AND 
    price_est.municipality_id = _municipality_id AND 
    price_est.county_id = _county_id 
ORDER BY price_est.neighbourhood_id NULLS LAST 
LIMIT 1; 

注意NULLS LAST是德故障排序，所以它不是絕對必要的，但在這樣的情況下明確表達意圖是很好的。