翻譯內容使用哪裏有2種語言的順序（language =「enus」或i18n =「enus」）

Question

我有一個帶子查詢的查詢來獲取翻譯文本，但where子句不工作...
始終返回文本提供美式英語，因爲它是在DB的第一，即使其他語言

我該怎麼做才能尊重查詢所陳述的順序（語言=「美式英文」或國際化=「美式英文」）
首先ptbr else或enus

[翻譯]

key | language | text 
1 | enus  | foo in enus 
1 | ptbr  | foo in ptbr 
1 | it  | foo in it 

[查詢]

select 
    A.*, 
    (select text from translate where key = A.key and (language = "ptbr" or i18n = "enus") limit 1) `translate` 
from table as A 
where A.id = 1 

Answer 1

使用多個LEFT JOIN條款。

SELECT a.*, IFNULL(p.text, e.text) AS text 
FROM table AS a 
LEFT JOIN translate AS p ON p.key = a.key AND p.language = 'ptbr' 
LEFT JOIN translate AS e ON e.key = a.key AND e.i18n = 'enus' 

，將做你想做的子查詢：

SELECT text 
FROM (SELECT 1 AS priority, text 
     FROM translate 
     WHERE key = A.key 
     AND language = 'ptbr' 
     UNION 
     SELECT 2 AS priority, text 
     FROM translate 
     WHERE key = A.key 
     AND i18n = 'enus') x 
ORDER BY priority 
LIMIT 1 

或者你可以這樣做：

SELECT text 
FROM translate 
WHERE key = A.key 
AND (language = "ptbr" or i18n = "enus") 
ORDER BY language = "ptbr" DESC 
LIMIT 1 

的普遍觀點是，如果你想LIMIT 1返回優選排，您需要使用ORDER BY以確保該行在結果中處於第一位。