MS SQL - One to Many Relationship - Need to return single row

Question

I have the following tables -

Search Result
----------------
SearchResultID PK
ProductID FK
SearchQuery
WebsiteName
URL
IsFound
CreatedOn
BatchID
Name

SearchResultItem
-----------------
SearchResultItemID PK
SearchResultID FK
Name
Value

These tables have a one to many relationship, so one Search Result, can have many Search Result Items.

I can do an INNER JOIN on these tables however that obviously gives one row per each Search Result Item. Ideally I would like one row per Search Result, for example...

SearchResultID | ProductID | SearchQuery | WebsiteName | URL | IsFound | 
CreatedOn | BatchID | Name | SearchResultItemID | Name 1 | Value 1 | Name 2 | 
Value 2 | Name 3 | Value 3 |

Is this possible to do? And if so, can someone point me in the right direction as to how I would do this - I think it would be something like this, only in ms-sql - one to many sql select into single row - mysql

There are a number of ways to do it. Do you know before hand how many results you have or want? Do you want the information from each row concatenated together into one column or do you want a seperate column for each row? — David Söderlund, May 31 '13 at 11:16
Hi @DavidSöderlund , Ideally I'd like a separate column for each row, I could also know beforehand the number of results I needed, for e.g. I'd know that this query will have 3 sets of names/values.. — 109221793, May 31 '13 at 11:19

GarethD · Accepted Answer · 2013-05-31T11:37:37.813

You can use the ROW_NUMBER() function to give each search result item a rank within each search result:

SELECT  SearchResultItemID,
        SearchResultID,
        Name,
        Value,
        RowNumber = ROW_NUMBER() OVER(PARTITION BY SearchResultID ORDER BY SearchresultItemID)
FROM    SearchResultItem;

If you have a know number of items then you can use aggregate functions to get each name/value pair:

WITH RankedItem AS
(   SELECT  SearchResultItemID,
            SearchResultID,
            Name,
            Value,
            RowNumber = ROW_NUMBER() OVER(PARTITION BY SearchResultID ORDER BY SearchresultItemID)
    FROM    SearchResultItem
)
SELECT  SearchResultID,
        Name1 = MIN(CASE WHEN RowNumber = 1 THEN Name END),
        Value1 = MIN(CASE WHEN RowNumber = 1 then Value END),
        Name2 = MIN(CASE WHEN RowNumber = 2 THEN Name END),
        Value2 = MIN(CASE WHEN RowNumber = 2 then Value END),
        Name3 = MIN(CASE WHEN RowNumber = 3 THEN Name END),
        Value3 = MIN(CASE WHEN RowNumber = 3 then Value END),
        Name4 = MIN(CASE WHEN RowNumber = 4 THEN Name END),
        Value5 = MIN(CASE WHEN RowNumber = 4 then Value END)
FROM    RankedItem
GROUP BY SearchResultID;

You can then join this back to your Search result table giving a full query:

WITH RankedItem AS
(   SELECT  SearchResultItemID,
            SearchResultID,
            Name,
            Value,
            RowNumber = ROW_NUMBER() OVER(PARTITION BY SearchResultID ORDER BY SearchresultItemID)
    FROM    SearchResultItem
), Items AS
(   SELECT  SearchResultID,
            Name1 = MIN(CASE WHEN RowNumber = 1 THEN Name END),
            Value1 = MIN(CASE WHEN RowNumber = 1 then Value END),
            Name2 = MIN(CASE WHEN RowNumber = 2 THEN Name END),
            Value2 = MIN(CASE WHEN RowNumber = 2 then Value END),
            Name3 = MIN(CASE WHEN RowNumber = 3 THEN Name END),
            Value3 = MIN(CASE WHEN RowNumber = 3 then Value END),
            Name4 = MIN(CASE WHEN RowNumber = 4 THEN Name END),
            Value4 = MIN(CASE WHEN RowNumber = 4 then Value END)
    FROM    RankedItem
    GROUP BY SearchResultID
)

SELECT  SearchResult.SearchResultID,
        SearchResult.ProductID,
        SearchResult.SearchQuery,
        SearchResult.WebsiteName,
        SearchResult.URL,
        SearchResult.IsFound,
        SearchResult.CreatedOn,
        SearchResult.BatchID,
        SearchResult.Name,
        Items.Name1,
        Items.Value1,
        Items.Name2,
        Items.Value2,
        Items.Name3,
        Items.Value3,
        Items.Name4,
        Items.Value4
FROM    SearchResult
        INNER JOIN Items
            ON SearchResult.SearchResultID = Items.SearchResultID;

Example on SQL Fiddle

If you want to return a variable number of values then you will need to use dynamic SQL:

DECLARE @SQL NVARCHAR(MAX) = '';

SELECT  @SQL = @SQL + ',[Name' + rn + '], [Value' + rn + '] '
FROM    (   SELECT  DISTINCT
                    rn = CAST(ROW_NUMBER() OVER(PARTITION BY SearchResultID ORDER BY SearchresultItemID) AS VARCHAR)
            FROM    SearchResultItem
        ) p;

SET @SQL = 'WITH RankedItem AS
            (   SELECT  SearchResultItemID,
                        SearchResultID,
                        Name,
                        Value,
                        RowNumber = ROW_NUMBER() OVER(PARTITION BY SearchResultID ORDER BY SearchresultItemID)
                FROM    SearchResultItem
            ), UnPivoted AS
            (   SELECT  upvt.SearchResultID,
                        Name = upvt.n + CAST(RowNumber AS VARCHAR),
                        upvt.v
                FROM    RankedItem
                        UNPIVOT
                        (   n
                            FOR v IN ([Name], [Value])
                        ) upvt
            ), Pivoted AS
            (   SELECT  *
                FROM    UnPivoted
                        PIVOT
                        (   MAX(V)
                            FOR Name IN (' + STUFF(@SQL, 1, 1, '') + ')
                        ) pvt
            )
            SELECT  SearchResult.SearchResultID,
                    SearchResult.ProductID,
                    SearchResult.SearchQuery,
                    SearchResult.WebsiteName,
                    SearchResult.URL,
                    SearchResult.IsFound,
                    SearchResult.CreatedOn,
                    SearchResult.BatchID,
                    SearchResult.Name' + @SQL + '                       
            FROM    SearchResult
                    INNER JOIN Pivoted
                        ON SearchResult.SearchResultID = Pivoted.SearchResultID;';

EXECUTE SP_EXECUTESQL @SQL;

Example on SQL Fiddle

N.B. I have intentionally used a different way of doing this in dynamic sql just to show there is more than one way to achieve the result of combining the rows.

MS SQL - One to Many Relationship - Need to return single row

1 Answers1