选择内连接4表

Question

so i want to get a specific data from table number 4 which is interconnected to the other 3 table the user will choose the $faid and will print the data needed

table 1 (dbo.FAID)
FAID(pk)
PCID(fk)
UserID(fk)

table 2 (dbo.users)
UserID(PK)
EmployeeName

table 3(dbo.SubDeptTransfer)
TransferID(pk)
UserID(fk)
SubDeptID(fk)

table 4 (SubDept)
SubDeptID(PK)
DeptID(fk)

table 5(department)
DeptID(PK)
Department

<?php
$faidf=$_POST['faidf'];
ini_set("display_errors","on");
$conn = new COM("ADODB.Connection");
   try {
   $myServer = "WTCPHFILESRV\WTCPHINV";
   $myUser = "sa";
   $myPass = "P@ssw0rd";
   $myDB = "wtcphitinventory";   
   $connStr = "PROVIDER=SQLOLEDB;SERVER=".$myServer.";UID=".$myUser.";PWD=".$myPass.";DATABASE=".$myDB;
   $conn->open($connStr); 
         if (! $conn) {
            throw new Exception("Could not connect!");
        }
   }

   catch (Exception $e) {
      echo "Error (File:): ".$e->getMessage()."<br>";
   }
if (!$conn)
  {exit("Connection Failed: " . $conn);}
  echo "<center>";
   echo "<table border='0' width ='100%' style='margin-left:90px'><tr><th></th><th></th></tr>";
   $sql_exp = "SELECT  e.Department
FROM    dbo.FA_PC a
        INNER JOIN dbo.users b
        on a.UserID = b.UserID
        INNER JOIN dbo.SubDeptTransfer c
            ON a.UserID = c.UserID  
        INNER JOIN dbo.SubDept d
            ON a.SubDeptID = d.SubDeptID
        INNER JOIN dbo.department e
            ON a.DeptID = e.DeptID
WHERE   a.FAID = $faidf";    
   $rs = $conn->Execute($sql_exp);  

    echo "<tr><td>".$rs->Fields("Department")."</tr></td>";
       $rs->Close();   

?>

all i could get is "Invalid column name 'SubDeptID" which is im certain that the column name is correct though i think i mess up with my select statement

FAID->users->subdepttransfer->subdept->department

is there any conflict of how many inner joins has been made or it cannot execute more than 3 tables? if yes is there any way to connect the 5 tables?

Answer 1

There is no restriction AFAIK, at least 5 tables should not be a problem. In your case there is a typo in the SQL statement. You use alias a, but i think you meant to use c (I have also fixed the DeptID - your next error after you fix the SubDeptID). Try this statement

SELECT  e.Department
FROM    dbo.FA_PC a
        INNER JOIN dbo.users b
        on a.UserID = b.UserID
        INNER JOIN dbo.SubDeptTransfer c
            ON a.UserID = c.UserID  
        INNER JOIN dbo.SubDept d
            ON c.SubDeptID = d.SubDeptID
        INNER JOIN dbo.department e
            ON d.DeptID = e.DeptID
WHERE   a.FAID = $faidf