Updating row of table Using data from multiple columns of another table - sql

Question

I have following table which I want to update using another table, given below.alt text http://img94.imageshack.us/img94/4602/leisureoriginal.png
I want to update Null values of above given table using following table on the basis of ProductId.
alt text http://img264.imageshack.us/img264/512/datatable2.png
The updated table should be like this.
alt text http://img690.imageshack.us/img690/9585/updatedtable.png
I have mentioned ProductId in these table just for example. I don't know exact ProductId. It could be any ProductId.
I know FieldId and FieldValue in advance in 2nd table.
Can I do this in one UPDATE statement for all columns.

Answer 1

In SQL Server, the PIVOT keyword turns rows into columns. We need two PIVOTs, one for FieldId and one for FieldValue. The ;WITH keyword (which is preceded by a semicolon to distinguish it from the unrelated WITH ROLLUP command) allows us to use create "temporary views" which we use later in the UPDATE statement.
;WITH FieldIds AS (SELECT * FROM (SELECT ProductId, FieldId FROM ProductFields) A
PIVOT (MAX(FieldId) FOR FieldId IN ([50], [55], [60])) AS B),
FieldValues AS (SELECT * FROM ProductFields
PIVOT (MAX(FieldValue) FOR FieldId IN ([50], [55], [60])) AS C)
UPDATE Products
SET
RatingId = FieldIds.[50],
Rating = FieldValues.[50],
LeisureId = FieldIds.[55],
Leisure = FieldValues.[55],
SpaId = FieldIds.[60],
Spa = FieldValues.[60]
FROM Products
INNER JOIN FieldIds ON FieldIds.ProductId = Products.ProductId
INNER JOIN FieldValues ON FieldValues.ProductId = Products.ProductId

Answer 2

In SQL Server, an UPDATE statement allows a FROM clause with JOINS. For example, this query would update the Rating field:
UPDATE p
SET p.Rating = pf.FieldValue
FROM Products p
INNER JOIN ProductField pf
ON pf.ProductId = p.ProductId
WHERE pf.FieldId = 50
You could copy this query for the other fields. It's also possible to update more fields in query, but that seems unnecessary in this case.

Answer 3

You will first need to transform your second table so that it contains only one row per ProductID.
SELECT t1.ProductID, t1.FieldID AS RatingID, t1.FieldValue AS Rating,
t2.FieldID AS LeisureID, t2.FieldValue AS Leisure, etc.
FROM SecondTable t1
LEFT OUTER JOIN SecondTable t2
ON t1.ProductID = t2.ProductID
AND t2.FieldValue = 55
LEFT OUTER JOIN SecondTable t3
ON t1.ProductID = t3.ProductID
AND t3.FieldValue = 60
WHERE t1.FieldValue = 50
Then you can update all columns in the first table from this table in one update query. Note that you could make the above a View of the Second table so this would be easier to use later. (We'll call it SecondTableView for now; incidentally it has the exact form of the first table now).
UPDATE FirstTable
SET RatingID = t1.RatingID, Rating = t1.Rating, etc.
FROM SecondTableView t1
WHERE FirstTable.ProductID = t1.ProductID
The issue with this approach is that you must know all of the possible Fields for each Product ahead of time but that is pretty much required anyway because of the table schema being fixed.

Answer 4

Maybe something like this:
Update T1
Set T1.RatingID = T2.FieldID,
T1.Rating = T2.FieldValue
From Table1 T1
Inner JOin Table2 T2
On T1.ProductID = T2.ProductID
Where T2.FieldID = 50
To edit all the columns at once, you would need to use subqueries:
Update T1
Set T1.RatingID = (Select T2.FieldID
From Table2 T2
Where T2.FieldID = 50
And T2.ProductID = T1.ProductID)
From Table1 T1