Question

I have a table with columns

Index, Date

where an Index may have multiple Dates, and my goal is the following: select a list that looks like

Index, MinDate, MaxDate

where each Index is listed only once, and MinDate (MaxDate) represents the earliest (latest) date present in the entire table for that index. That’s easy enough, but then let’s constrain this list to appear only for Indexes that are present in a given range of dates.

So far, I have the following:

SELECT      Index,     MIN([Date]),     MAX([Date]) FROM myTable WHERE     Index IN     (SELECT Index From myTable WHERE [Date] BETWEEN '1/1/2000' AND '12/31/2000') GROUP BY Index ORDER BY Index ASC 

This is excruciatingly slow. Any way to speed this up? [I am running SQL Server 2000.]

Thanks!

Edited: For clarity.

Answer 1

I would recommend a derived table approach. Like this:

SELECT       myTable.Index,      MIN(myTable.[Date]),      MAX(myTable.[Date]) FROM myTable      Inner Join (        SELECT Index         From myTable         WHERE [Date] BETWEEN '1/1/2000' AND '12/31/2000') As AliasName        On myTable.Index = AliasName.Index GROUP BY myTable.Index ORDER BY myTable.Index ASC 

EDIT: Upon further review, there is another way you can create this query. The following query may be faster, slower, or execute in the same amount of time. This, of course, depends on how the table is indexed.

Select [Index],        Min([Date]),        Max([Date]) From   myTable Group By [Index] Having Sum(Case When [Date] Between '1/1/2000' And '12/31/2000' Then 1 Else 0 End) > 0 

Under the best circumstances, this query will cause an index scan (not a seek) to filter out rows you don’t want to display. I encourage you to run both queries and pick this oen the executes the fastest.