Question

我正在尝试将多个表作为单个视图访问，但我没有匹配查询中的任何数据。我很确定问题出在视图声明中。

CREATE VIEW IF NOT EXISTS method_view 
AS SELECT 
 peercreateddata.id,
 peercreateddata.name,
 peercreateddata.shared,
 peercreateddata.authorHash,
 peercreateddata.creationDate,
 peercreateddata.firstSeen,
 peercreateddata.lang,
 methods.primaryMatch,
 methods.methodHash,
 methods.methodbyline,
 methods.methodexpirationDate,
 methods.methodlocation,
 localResources.localmimeType,
 remoteResources.remotemimeType,
 remoteResources.remotelocation 

FROM peercreateddata peercreateddata,
 methods methods,
 localResources localResources,
 remoteResources remoteResources 

WHERE (methods.peerDataId = peercreateddata.id) 
      AND (localResources.localMethodId = methods.id) 
      AND (remoteResources.remoteMethodId = methods.id) ;

查看WHERE子句，methods.peerDataId始终匹配peercreateddata.id的单个值。表localResources和remoteResources有时是空的，有时不包含查询匹配，有时包含多个匹配。

我正在为Android开发。语法传递验证器（尽管有人抱怨使用名为'name'的字段）。

Answer 1

使用内部和外部联接子句。请参阅docs。

用这个替换你的from子句并摆脱where

FROM peercreateddata peercreateddata
 inner join methods methods 
       on methods.peerDataId = peercreateddata.id
 left outer join localResources localResources 
       on localResources.localMethodId = methods.id
 left outer join remoteResources remoteResources 
       on  remoteResources.remoteMethodId = methods.id

通过视图访问多个表

1 个答案: