Question

https://i.stack.imgur.com/ZRH9c.jpg (请见数据库结构实例图)

至今

我试图在两张表格中打字,这两张表格开始用具体信函,我不知道如何加入。

www.un.org/spanish/ecosoc 如果NOT在“用户_vocabulary”中给出了一种真心的字眼,我想从用户_vocabulary中删除这一词,但如果存在一种真心_,我想读到“系统_vocabulary”WHERE用户_vocabulary.voc_id=system.vocabulary.id .的所有数据。

This I use to just read one table (just for your information): SELECT * FROM user_vocabulary WHERE word LIKE $user_input% ORDER BY word ASC

我发现一些类似员额,但似乎无法将这些员额转为这一问题。

Any help is much appreciated. cheers Tom

Answer 1

页: 1 您可使用<代码>IF功能:

SELECT
  uv.id,
  IF(uv.voc_id = 0,uv.word,sv.word) AS WORD
FROM user_vocabulary uv
LEFT JOIN system_vocabulary sv
ON (uv.voc_id = sv.id)
HAVING word LIKE  %user_input% 

+------+-------+
| id   | word  |
+------+-------+
|    1 | hat   |
|    2 | home  |
|    3 | hello |
+------+-------+
3 rows in set (0.00 sec)

Answer 2

引言

SELECT *
FROM user_vocabulary
left join system_vocabulary
on system_vocabulary.voc_id = user_vocabulary.id
WHERE user_vocabulary.word LIKE  %$user_input%  or system_vocabulary.word like      %$user_input% 
ORDER BY word ASC

EDITED

另一种方式

SELECT *
FROM user_vocabulary as uv
, system_vocabulary as sv
WHERE uv.word LIKE  %$user_input% 
or sv.word like  %$user_input%

Answer 3

根据您的要求开展工作:

SELECT user_vocabulary.id,
   COALESCE(system_vocabulary.word, user_vocabulary.word) word
FROM user_vocabulary
LEFT JOIN system_vocabulary
   ON system_vocabulary.id = voc_id AND voc_id <> 0

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