SQL Server : multiple join query optimization - sql-server

Question

I've just started with Microsoft SQL Server and I'm facing a problem, which I believe it is an sql optimization issue. Could you please take a look (see below) and give me your feedback.
I have two tables defined as follows:
floatTable (DateAndTime datetime2(7),
TagIndex smallint,
Val float)
stringTable (DateAndTime datetime2(7),
TagIndex smallint,
Val float)
The SQL query which I have used to get the RESULT is (don't laugh):
DECLARE #startDate DATETIME, #endDate DATETIME
SET #startDate = '20130312 9:00:00'
SET #endDate = '20130313 9:00:00'
USE TensionDB
SELECT t1.DateAndTime, t1.Val AS Winch_1,t2.Val AS Winch_2, t3.Val AS Winch_3, t4.Val AS Winch_4, t5.Val AS Winch_5,
t6.Val AS Winch_6, t7.Val AS Winch_7, t8.Val AS Winch_8, t9.Val AS Latitude, t10.Val AS Longitude
FROM
((SELECT DISTINCT DateAndTime ,Val FROM dbo.FloatTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 0)t1
INNER JOIN (SELECT DISTINCT DateAndTime,Val FROM dbo.FloatTable
WHERE ( DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 1)t2
ON t2.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime,Val FROM dbo.FloatTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 2)t3
ON t3.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime,Val FROM dbo.FloatTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 3)t4
ON t4.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime,Val FROM dbo.FloatTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 4)t5
ON t5.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime,Val FROM dbo.FloatTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 5)t6
ON t6.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime,Val FROM dbo.FloatTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 6)t7
ON t7.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime,Val FROM dbo.FloatTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 7)t8
ON t8.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime, Val FROM dbo.StringTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 8)t9
ON t9.DateAndTime = t1.DateAndTime
INNER JOIN (SELECT DISTINCT DateAndTime, Val FROM dbo.StringTable
WHERE (DateAndTime BETWEEN #startDate AND #endDate) AND TagIndex = 9)t10
ON t10.DateAndTime = t1.DateAndTime)
PROBLEM: The big problem is that even if I get the correct result, the query gets very slow for large amount of data. I'm pretty sure that there is another way to write the query, but for the moment I don't have any other idea.
Could you give me a hint please? Appreciate any help from your side.
Thank you in advance
#Kiril and #Patrick,
Using your hints and ideas I have re-wrote my original query using pivot table.
Unfortunately, I still have to use INNER JOIN, as the values(Val) in the stringTable are strings and values(Val) in floatTable are floats. To be honest, I have to perform more tests with both queries, as I can't see a real improvement (time wise), using pivot table; apart from the length of the query. One last thing, I have embedded the query in a stored procedure. Please find below the "final" code:
-- ================================================
-- Template generated from Template Explorer using:
-- Create Procedure (New Menu).SQL
--
-- Use the Specify Values for Template Parameters
-- command (Ctrl-Shift-M) to fill in the parameter
-- values below.
--
-- This block of comments will not be included in
-- the definition of the procedure.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: xxxx
-- Create date: xxxx
-- Description: retrieves tension data
-- =============================================
CREATE PROCEDURE getTension
-- Add the parameters for the stored procedure here
#startDate datetime = NULL,
#endDate datetime = NULL
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for procedure here
SELECT distinct pvt.DateAndTime
, pvt.[0] AS Winch_1
, pvt.[1] AS Winch_2
, pvt.[2] AS Winch_3
, pvt.[3] AS Winch_4
, pvt.[4] AS Winch_5
, pvt.[5] AS Winch_6
, pvt.[6] AS Winch_7
, pvt.[7] AS Winch_8
, st.Val AS Longitude
, st1.Val AS Latitude
FROM FloatTable
PIVOT
(MAX(Val)
FOR TagIndex in ([0],[1],[2],[3],[4],[5],[6],[7])
) as pvt
inner join StringTable st on st.DateAndTime = pvt.DateAndTime and st.TagIndex = 8
inner join StringTable st1 on st1.DateAndTime = pvt.DateAndTime and st1.TagIndex = 9
Where (pvt.DateAndTime between #startDate and #endDate)
ORDER BY DateAndTime
END
GO
Thanks again for your guidance

Answer 1

I suppose that using pivot table is going to be more efficient:
DECLARE #startDate DATETIME, #endDate DATETIME
SET #startDate = '20130312 9:00:00'
SET #endDate = '20130313 9:00:00'
SELECT st.DateAndTime
, pvt.0 AS Winch_1
, pvt.1 AS Winch_2
, pvt.2 AS Winch_3
, pvt.3 AS Winch_4
, pvt.4 AS Winch_5
, pvt.5 AS Winch_6
, pvt.6 AS Winch_7
, pvt.7 AS Winch_8
, pvt.8 AS Latitude
, pvt.9 AS Longitude
FROM StringTable st
INNER JOIN FloatTable ft on st.DateandTime=ft.DateandTime
pivot
( MAX(Val) for [TagIndex] in ([0], [1], [2], [3], [4], [5], [6], [7], [8], [9])
order by [st.DateAndTime]
)pvt
I haven't tested it so you may have to tweak it a bit, in order to make it work.

Answer 2

Start putting DateAndTime and TagIndex in an index. That would make a difference.
On the other hand, your query could get a lot faster if you wouldn't need the repeating inner joins.
Can you replace the distinct by a single group by and use min or max?
Another option is using pivot tables.
Like this:
select *
from FloatTable
pivot (min(DateAndTime) x, min(Val) y in ([1],[2],[3], ...))