Question

UPDATE
    dbo.FormDetail
SET 
    FieldOrder=FieldOrder+1
WHERE
    WHERE DocCode IN (1,2,3)
    AND FieldOrder >= (SELECT FieldOrder FROM dbo.FormDetail
                       WHERE FieldData LIKE '%OldField%'
                       AND DocCode IN (1,2,3))

Don’t know how clear it is what I’m trying to do here but I want to increase the FieldOrder in the FormDetail table for a number of documents but only after a certain field (basically so I have a gap to insert a new field). But the obvious problem is that the FieldOrder I get in my Where will not be specific to the document that the statement may currently be updating. I was thinking it’s probably possible using partitions but I have only ever used partitions in From sections. Any help would be really appreciated.

UPDATE

dbo.FormDetail Sample Data

DocCode FieldOrder FieldData

1 1 ‘Title’

1 2 ‘OldField’

1 3 ‘Signature’

2 1 ‘Paragraph’

2 2 ‘OldField’

3 1 ‘OldField’

Answer 1

In your existing code your sub-query is executed once and returns all it’s results in one go to your outer query.

What you actually appear to want is for the sub-query to be executed once for every row being processed by the outer query. The is called a correlated sub-query.

To make it work like that I have made two changes;
1. I’ve given the table an alias in the sub-query
2. I’ve changed the sub-query WHERE clause to reference the table in the outer-query

UPDATE
  dbo.FormDetail
SET
  FieldOrder=FieldOrder+1
WHERE
  DocCode IN (1,2,3)
  AND FieldOrder >= (SELECT lookup.FieldOrder
                       FROM dbo.FormDetail AS lookup
                      WHERE lookup.FieldData LIKE '%OldField%'
                        AND lookup.DocCode = FormDetail.DocCode
                    )

Another alternative could be to join on a sub-query…

UPDATE
  FormDetail
SET
  FieldOrder=FieldOrder+1
FROM
  dbo.FormDetail
INNER JOIN
(
  SELECT
    DocCode,
    FieldOrder
  FROM
    dbo.FormDetail
  WHERE
    DocCode IN (1,2,3)
    AND FieldData LIKE '%OldField%'
)
  AS lookup
    ON  lookup.DocCode     = FormDetail.DocCode
    AND lookup.FieldOrder >= FormDetail.FieldOrder