SQL only want to return a single row for each note
I have the following tables: Orders, Notes, Permits
The following columns are in each table:
Orders = ID
Notes = ID, RelatedID, Note, Timestamp
Permits = ID, OrderId
I have the following query
SELECT o.id
, op.id
, n.timestamp
FROM [tblOrders] o
INNER JOIN [tblNotes] n ON n.[RelatedID] = o.[ID]
INNER JOIN [tblPermits] op ON o.[id] = op.[OrderID]
WHERE n.[Text] LIKE 'Line item is created%'
An order has 1 to many permits and a order has 1 to many notes
The problem here is that the notes relate to the order and not the individual permit so when you join o.id with n.relatedID if there is more that 1 permit in an order it will actually show 4 records instead of 2 since it joins twice for each permit开发者_开发知识库 since the orderID is the same. How can I get this to only return 2 records?
The issue is using JOINs risks duplication in the resultset because there'll be a record for each supporting record in the tblnotes
. My first recommendation is to re-write so you aren't using a JOIN:
Using EXISTS:
SELECT o.id,
p.id
FROM tblorders o
JOIN tblpermits p ON p.orderid = o.id
WHERE EXISTS(SELECT NULL
FROM tblnotes n
WHERE n.[Text] LIKE 'Line item is created%'
AND n.relatedid = o.id)
Using IN:
SELECT o.id,
p.id
FROM tblorders o
JOIN tblpermits p ON p.orderid = o.id
WHERE o.id IN (SELECT n.relatedid
FROM tblnotes n
WHERE n.[Text] LIKE 'Line item is created%')
One way would be
SELECT DISTINCT
o.id
,op.id
.....
....
SELECT o.id ,op.id
FROM [tblOrders] o
JOIN [tblPermits] op
ON op.[OrderID] = o.[id]
WHERE o.id IN
(
SELECT n.[RelatedID]
FROM tblNotes n
WHERE n.[Text] LIKE 'Line item is created%'
)
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