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I'm trying to SELECT, and get a unique result set, from a MySQL database, as shown below. My problem is, I think, I don't understand LEFT Joins well enough. Or, maybe I need to use a different Join approach.

Here's a description of the database.

tbAdult (Adults) have x number of tbchild (Children) , and uses a cross-ref table called tbadultchildxref. This table has an f-key to both Adult and Child. I have to use an x-ref table, because there's a many-to-many relationship between these two tables, and there's other data that's keep in the x-ref, which I have removed for simplicity.

In turn, each Child belongs to a Program (tblprogram).

Each Program has x number of Cameras (tblCamera). Again, I have to use an x-ref table between tblProgram and tblCamera due to a many-to-many relationship, and other reasons.

What I am trying to get at, is a unique list of Cameras for a given Parent.

For example, Parent 675 has three children, Child ID's 789,788, and 789. Those three children, in turn, belong to Program ID's 4, 5, and 6.

Program ID 4 has Camera ID's 1,2,3 Program ID 5 has Camera ID's 4,5,6 Program ID 6 has Camera ID's 1,6,7,8

What I would like the result set to be is 1,2,3,4,5,6,7,8

I have tried different combinations of SELECT DISTINCT, LEFT JOINS on the various x-ref tables, etc. but I just can't seem to get it.

My other problem, along the way, is I need to check the "Active" fields in Adult, Child, and Program to equal = 1 (true) for the result set.

Thanks in advance.

CREATE TABLE `tbladult` (
 `pkAdultID` int(11) NOT NULL AUTO_INCREMENT,
 `fldAdultActive` tinyint(1) DEFAULT '1',
 `fldAdultLogin` varchar(30) DEFAULT NULL,
 `fldAdultPassword` varchar(45) DEFAULT NULL,
 `fldAdultFirstName` varchar(60) DEFAULT NULL,
 `fldAdultLastName` varchar(60) DEFAULT NULL,
 PRIMARY KEY (`pkAdultID`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;


/*Table structure for table `tblchild` */

CREATE TABLE `tblchild` (
 `pkChildID` int(11) NOT NULL AUTO_INCREMENT,
 `fldChildActive` tinyint(4) DEFAULT NULL,
 `fldChildFirstName` varchar(45) DEFAULT NULL,
 `fldChildLastName` varchar(45) DEFAULT NULL,
 `fkChildProgram` int(1) DEFAULT NULL,
 PRIMARY KEY (`pkChildID`),
 KEY `FK_tblchild` (`fkChildProgram`),
 CONSTRAINT `FK_tblchild` FOREIGN KEY (`fkChildProgram`) REFERENCES `tblprogram` (`pkProgramID`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;


/*Table structure for table `tbladultchildxref` */

CREATE TABLE `tbladultchildxref` (
 `pkAdultChildxRefID` int(11) NOT NULL AUTO_INCREMENT,
 `fldAdultChildxRefActive` tinyint(1) DEFAULT '1',
 `fkAdultID` int(11) DEFAULT NULL,
 `fkChildID` int(11) DEFAULT NULL,
 PRIMARY KEY (`pkAdultChildxRefID`),
 KEY `FK_tbladultchildxref` (`fkAdultID`),
 KEY `FK_tbladultchildxref2` (`fkChildID`),
 CONSTRAINT `FK_tbladultchildxref` FOREIGN KEY (`fkAdultID`) REFERENCES `tbladult` (`pkAdultID`),
 CONSTRAINT `FK_tbladultchildxref2` FOREIGN KEY (`fkChildID`) REFERENCES `tblchild` (`pkChildID`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;



/*Table structure for table `tblprogram` */

CREATE TABLE `tblprogram` (
  `pkProgramID` int(11) NOT NULL AUTO_INCREMENT,
  `fldProgamActive` tinyint(1) DEFAULT '1',
  `fldProgramName` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`pkProgramID`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=latin1;

/*Table structure for table `tblcamera` */

CREATE TABLE `tblcamera` (
 `pkCameraID` int(11) NOT NULL AUTO_INCREMENT,
 `fldCameraName` varchar(50) DEFAULT NULL,
 `fldCameralocation` varchar(50) DEFAULT NULL,
 `fldCameraURL` varchar(250) DEFAULT NULL,
 PRIMARY KEY (`pkCameraID`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=latin1;


/*Table structure for table `tblprogramcameraxref` */

CREATE TABLE `tblprogramcameraxref` (
 `pkProgramCameraXrefID` int(11) NOT NULL AUTO_INCREMENT,
 `fkProgramID` int(11) DEFAULT NULL,
 `fkCameraID` int(11) DEFAULT NULL,
 PRIMARY KEY (`pkProgramCameraXrefID`),
 KEY `FK_tblprogramcameraxref` (`fkProgramID`),
 KEY `FK_camerasforprograms` (`fkCameraID`),
 CONSTRAINT `FK_camerasforprograms` FOREIGN KEY (`fkCameraID`) REFERENCES `tblcamera`     (`pkCameraID`),
 CONSTRAINT `FK_tblprogramcameraxref` FOREIGN KEY (`fkProgramID`) REFERENCES `tblprogram` (`pkProgramID`)
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2 回答 2

3

不需要左连接：

SELECT DISTINCT tblprogramcameraxref.fkcameraid
FROM tblprogramcameraxref
JOIN tblprogram ON tblprogramcameraxref.fkprogramid = tblprogram.pkprogramid
  AND tblprobram.fldProgramActive = 1
JOIN tblchild ON tblprogramcameraxref.fkprogramid = tblchild.fkchildprogram 
  AND tblchild.fldChildActive = 1
JOIN tbladultchildxref ON tblchild.pkchildid = tbladultchildxref.fkchildid
  AND tbladultchildxref.fldAdultChildxRefActive = 1
WHERE tbladultchildxref.fkadultid = 675

此外，您可能需要检查fkChildProgram int(1) DEFAULT NULL,in tblchild - 它引用的列定义为int(11)

此时，您实际上不需要检查 Adult 是否处于活动状态（因为这是您开始使用的搜索条件），但如果必须 - 只需将其添加到连接列表的末尾：

JOIN tbladult ON tbladultchildxref.fkadultid = tbladult.pkadultid
  AND tbladult.fldAdultActive = 1
于 2012-05-21T18:20:58.653 回答
0

这是一个很长的描述。如果我正确理解了这个问题，这个查询应该可以帮助你 -

SELECT DISTINCT pcref.fkCameraID
FROM tbladult adult,
     tblchild child,
     tbladultchildxref acref,
     tblprogram prog,
     tblcamera camera,
     tblprogramcameraxref pcref
WHERE adult.pkAdultID = 675
AND adult.fldAdultActive = TRUE
AND adult.pkAdultID = acref.fkAdultID
AND acref.fkChildID = child.pkChildID 
AND child.fldChildActive = TRUE
AND child.fkChildProgram = prog.pkProgramID 
AND prog.fldProgamActive = TRUE
AND prog.pkProgramID = pcref.fkProgramID
于 2012-05-21T18:22:23.977 回答