SQL Pivot-动态列，无聚合

Question

I'm trying to do a Pivot, but I'm not very experienced with pivots and I'm stuck - I can't figure out how to structure the query.

What I have:

• Data Types (types of measurements that are recorded)
• Locations
• Data Sources (things at each location that will be measured)
• Data Readings (measurements of the sources)

Additional information:

• The number of Sources at any one Location can change
• There will never be more than 5 sources at a single Location
• Only 1 Reading is saved per Source/Type/date

In the returned table:

• Table shows Data_Type info and Readings for a single Location and date
• Columns: Data_Name, Units, Is_Required (from Data_Type table), plus one column for each Source
• Rows: one row for each Data_Type
• Rows should be ordered by Type_Display_Order
• Sources (extra columns) should be ordered by Source_Display_Order
• Some Readings are optional, and some Sources aren't measured daily - these still need to be included in the table

Example:

Table: Data_Type
Data_Type_ID  Data_Name  Units  Is_Required (BIT)  Type_Display_Order
-----------------------------------------------------------------------
1             Height     In.    1                  2
2             Length     In.    0                  3
3             Weight     Lbs.   1                  1

Table: Location
Location_ID  Location
-----------------------
1            West
2            East

Table: Data_Source
Data_Source_ID  Location_ID  Source_Name  Source_Display_Order
----------------------------------------------------------------
1               1            WCS          2
2               2            ECS          1
3               1            WBN          1

Table: Data_Reading
Data_Reading_ID  Data_Type_ID  Data_Source_ID  Reading  Reading_Date
----------------------------------------------------------------------
1                1             1               5        6/3/2016
2                3             2               3        5/1/2016
3                1             1               7        5/1/2016
4                2             3               2        6/3/2016
5                3             1               4        6/3/2016

Desired results from query for Location = "West", Date = 6/3/2016:

Data_Type_ID  Data_Name  Units  Is_Required  WBN   WCS
---------------------------------------------------------
3             Weight     Lbs.   1            NULL  4
1             Height     In.    1            NULL  5
2             Length     In.    0            NULL  NULL

This solution seems to be similar: Pivot Dynamic Columns, no Aggregation but I'm still having some problems.

This is what I have so far:

DECLARE @date DATE, @locationID INT

SET @date = CAST('6/3/2016' AS DATE)
SET @locationID = 1

DECLARE @cols AS NVARCHAR(MAX), @query AS NVARCHAR(MAX)

SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(s.Source_Name)
            FROM Data_Source s
            WHERE s.Location_ID = @locationID
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)')
        ,1,1,'')

SET @query = 'SELECT Data_Type_ID, Data_Name, Units, Is_Required, ' + @cols +
' FROM
(
    SELECT
          t.Data_Type_ID
        , t.Data_Name
        , t.Units
        , t.Is_Required
        , r.Reading
        , s.Source_Name
    FROM
        Data_Type t
    LEFT JOIN
        Data_Reading r ON t.Data_Type_ID = r.Data_Type_ID
    LEFT JOIN
        Data_Source s ON r.Data_Source_ID = s.Data_Source_ID
    WHERE
        r.Reading_Date = CAST(CAST(' + @date + ' AS NVARCHAR(10)) AS DATE)
        AND s.Location_ID = CAST(' + @locationID + ' AS INT)
) x
PIVOT
(
    MIN(Reading)
    for Source_Name in (' + @cols + ')
) p '

I have the query working properly now, but I still have a few problems:

• @cols is not sorted by Source_Display_Order
• rows are not sorted by Type_Display_Order (I did have ORDER BY in the inner SELECT statement for part X, but I was getting errors saying I can't have an ORDER BY clause there)
• Date comparison in WHERE statement doesn't work - for some reason, it always computes as False, even when the dates are the same

Answer 1

Solved!

DECLARE @date DATE, @locationID INT

SET @date = CAST('6/3/2016' AS DATE)
SET @locationID = 1

DECLARE @cols AS NVARCHAR(MAX), @query AS NVARCHAR(MAX)

SET @cols = STUFF((SELECT ',' + QUOTENAME(s.Source_Name)
            FROM Data_Source s
            WHERE s.Location_ID = @locationID
            ORDER BY s.Source_Display_Order
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)')
        ,1,1,'')

SET @query =
'SELECT
      Data_Type_ID
    , Data_Name
    , Units
    , Is_Required
    , ' + @cols + '
FROM
(
    SELECT
          t.Data_Type_ID
        , t.Data_Name
        , t.Units
        , t.Is_Required
        , r.Reading
        , s.Source_Name
        , t.Type_Display_Order
    FROM
        Data_Type t
    LEFT JOIN
        Data_Reading r ON t.Data_Type_ID = r.Data_Type_ID
    LEFT JOIN
        Data_Source s ON r.Data_Source_ID = s.Data_Source_ID
    WHERE
        r.Reading_Date = ''' + CAST(@date AS NVARCHAR(10)) + '''
        AND s.Location_ID = ' + CAST(@locationID AS NVARCHAR(20)) + '
) x
PIVOT
(
    MIN(Reading)
    for Source_Name in (' + @cols + ')
) p
ORDER BY
    Type_Display_Order'

EXECUTE(@query)

To fix my problems:

• Convert @date to NVARCHAR before adding to @query string and include extra quotes to surround the new NVARCHAR in quotes within @query
• Remove DISTINCT clause from @cols and add ORDER BY (all of the names in my table are unique, so the DISTINCT is unnecessary)
• Add Type_Display_Order to the inner SELECT statement, and add ORDER BY after the PIVOT statement