I'm trying to run this SQL Expression in Access:
Select *
From ((TableA
Left Join TableB
On TableB.FK = TableA.PK)
Left Join TableC
On TableC.FK = TableB.PK)
Left Join (SELECT a,b,c FROM TableD WHERE b > 1) AS TableD
On (TableD.FK = TableC.PK AND TableA.a = TableD.a)
but it keeps getting error: Join-Expression not supported. Whats the problem? Sorry, im just starting with Jet-SQL and in T-SQL its all fine. Thanks
The issue is that the final outer join condition TableA.a = TableD.a
will cause the query to contain ambiguous outer joins , since the records to which TableA
is joined to TableD
will depend upon the results of the joins between TableA->TableB
, TableB->TableC
and TableC->TableD
.
To avoid this, you'll likely need to structure your query with the joins between tables TableA
, TableB
& TableC
existing within a subquery, the result of which is then outer joined to TableD
. This unambiguously defines the order in which the joins are evaluated.
For example:
select * from
(
select TableA.a, TableC.PK from
(
TableA left join TableB on TableA.PK = TableB.FK
)
left join TableC on TableB.PK = TableC.FK
) q1
left join
(
select TableD.a, TableD.b, TableD.c, TableD.FK from TableD
where TableD.b > 1
) q2
on q1.a = q2.a and q1.PK = q2.FK
Consider relating every join to the FROM
table to avoid having to nest relations.
SELECT *
FROM ((TableA
LEFT JOIN TableB
ON TableB.FK = TableA.PK)
LEFT JOIN TableC
ON TableC.FK = TableA.PK)
LEFT JOIN
(SELECT FK,a,b,c
FROM TableD WHERE b > 1
) AS TableD
ON (TableD.FK = TableA.PK)
AND (TableD.a = TableA.a)
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.