php - MySQL 查询使用 WHERE 连接表，包括匹配项和非匹配项

Question

以下查询将选举人的 ID 与来自投票意图的相应选举人匹配，以查找某些条件。

    "   FROM electors,voting_intention 
WHERE electors.ID = voting_intention.elector 
AND electors.telephone > 0 
AND electors.postal_vote != 1 
AND (mosaic IN ('E1','E2','E3') 
OR (voting_intention.pledge IN ('C','P') 
AND  voting_intention.election != '2012-07-05'))  "

问题在于该行AND (mosaic IN ('E1','E2','E3')，因为我们需要获取此信息，即使选举人.ID 和voting_intention.elector 之间不匹配，因为此信息在选举人表中。

这样做的方法是将这条线放在 WHERE 方程的首位。

Answer 1

您还可以做的是左外连接来选择所有记录，而不仅仅是完全连接的记录

WHERE electors.ID(+) = voting_intention.elector 

类似的东西......（未经测试）

Answer 2

这应该做！

FROM electors e
FULL OUTER JOIN votin_intention i
   ON e.ID=i.elector
WHERE electors.telephone > 0  
AND electors.postal_vote != 1  
AND (mosaic IN ('E1','E2','E3')  
OR (voting_intention.pledge IN ('C','P')  
AND  voting_intention.election != '2012-07-05'))  " 

Answer 3

会这样做吗:::

FROM electors,voting_intention WHERE electors.telephone > 0 AND electors.postal_vote != 1 AND (electors.mosaic IN ('E1','E2','E3') OR (electors.ID = voting_intention.elector AND voting_intention.pledge IN ('C','P') AND  voting_intention.election_date != '2012-07-05'))