谷歌的BigQuery：迭代是函數在子查詢

Question

讓我們假設我有兩個表：

girls  prefixes 
------  ---------- 
Le-na   -na  
Lo-ve   -ve 
Li-na   -la 
Lu-na   -ta 
Len-ka   -ya 

所有女生的名字和前綴長度不同！

我想要選擇包含前綴表的所有女孩的名字，並在查詢中做到這一點（假設我有很多名字和許多前綴）。

我未經測試，對單情況下，它正在完成這樣的：

SELECT girls,SOME(girls CONTAINS ("-na")) WITHIN RECORD FROM prefixes

但我怎麼實現在子查詢包含函數的迭代？ 例如

SELECT girls,SOME(girls CONTAINS (SELECT * FROM prefixes)) WITHIN RECORD FROM prefixes - 這不工作，造成子不能在SELECT子句

我真的很感激任何想法，我試圖尋找這一點，但找不到我的情況下允許的。

Answer 1

你剛剛使用過join嗎？

select * 
from girls g join 
    prefixes p 
    on g.girls like concat('%', p.prefix); 

這應該使用標準的SQL。

Answer 2

假設前綴（當然，後綴）總是三個字符，您可以執行與SUBSTR結果的有效半連接：

#standardSQL 
WITH Girls AS (
    SELECT name 
    FROM UNNEST(['Le-na', 'Lo-ve', 'Li-na', 'Lu-na', 'Len-ka']) AS name 
), 
Suffixes AS (
    SELECT suffix 
    FROM UNNEST(['-na', '-ve', '-la', '-ta', '-ya']) AS suffix 
) 
SELECT 
    name 
FROM Girls 
WHERE EXISTS (
    SELECT 1 FROM Suffixes WHERE suffix = SUBSTR(name, LENGTH(name) - 2) 
); 

或者你可以使用LIKE，但它相當於執行交叉帶過濾器聯接，所以它可能不會那麼快：

#standardSQL 
WITH Girls AS (
    SELECT name 
    FROM UNNEST(['Le-na', 'Lo-ve', 'Li-na', 'Lu-na', 'Len-ka']) AS name 
), 
Suffixes AS (
    SELECT suffix 
    FROM UNNEST(['-na', '-ve', '-la', '-ta', '-ya']) AS suffix 
) 
SELECT 
    name 
FROM Girls 
WHERE EXISTS (
    SELECT 1 FROM Suffixes WHERE name LIKE CONCAT('%', suffix) 
); 

編輯：

0：枚舉所有名稱後綴使用的半連接的另一種選擇

#standardSQL 
WITH Girls AS (
    SELECT name 
    FROM UNNEST(['Le-na', 'Lo-ve-lala', 'Li-na', 'Lu-eya', 'Len-ka']) AS name 
), 
Suffixes AS (
    SELECT suffix 
    FROM UNNEST(['-na', '-ve', '-lala', '-ta', '-eya']) AS suffix 
), 
GirlNamePermutations AS (
    SELECT name, SUBSTR(name, LENGTH(name) + 1 - len) AS name_suffix 
    FROM Girls 
    CROSS JOIN UNNEST(GENERATE_ARRAY(1, (SELECT MAX(LENGTH(suffix)) FROM Suffixes))) AS len 
) 
SELECT 
    name 
FROM GirlNamePermutations 
WHERE EXISTS (
    SELECT 1 
    FROM Suffixes 
    WHERE suffix = name_suffix 
); 

如果知道後綴長度的範圍，則可以改爲對其進行硬編碼，例如，更換：

CROSS JOIN UNNEST(GENERATE_ARRAY(1, (SELECT MAX(LENGTH(suffix)) FROM Suffixes))) AS len 

有：

CROSS JOIN UNNEST(GENERATE_ARRAY(1, 5)) AS len 

Answer 3

下面是BigQuery的標準SQL

#standardSQL 
WITH girls AS (
    SELECT name 
    FROM UNNEST(['Le-na', 'Lo-ve', 'Li-na', 'Lu-na', 'Len-ka']) AS name 
), 
suffixes AS (
    SELECT suffix 
    FROM UNNEST(['-na', '-ve', '-la', '-ta', '-ya']) AS suffix 
) 
SELECT name 
FROM girls 
JOIN suffixes 
ON ENDS_WITH(name, suffix) 

作爲一個選項 - 如果你需要擴展這個裏面找名片段 - 您可以使用REGEXP_CONTAINS

SELECT name 
FROM girls 
JOIN suffixes 
ON REGEXP_CONTAINS(name, suffix) 

或 - STARTS_WITH通過前綴匹配（vs.後綴）

SELECT name 
FROM girls 
JOIN suffixes 
ON STARTS_WITH(name, suffix)