Difficulty understanding difference

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Difficulty understanding difference

Author

Topic

Quimbly
Starting Member

4 Posts

Posted - 2007-02-26 : 14:10:11

These queries don't return the same results. Can someone explain why?

SELECT LuminiareRegionStaticMapID, RegionStaticMapID, LuminaireID, XPosition, YPosition FROM dbo.LuminairesRegionStaticMap
where LuminaireID in (SELECT luminaireID from LuminairesRegionStaticMap where RegionStaticMapID = 11)

select LuminiareRegionStaticMapID, RegionStaticMapID, LuminaireID, XPosition, YPosition FROM dbo.LuminairesRegionStaticMap
where RegionStaticMapID = 11

SwePeso
Patron Saint of Lost Yaks

30421 Posts

Posted - 2007-02-26 : 14:33:18

First query matches on LuminaireID and second query matches on RegionStaticMap.

Peter Larsson
Helsingborg, Sweden

Quimbly
Starting Member

4 Posts

Posted - 2007-02-26 : 14:57:57

Ahh, I've discovered the answer myself.

The answer is, there is no difference, unless the LuminairesRegionStaticMap table has rows with duplicate LuminaireID values. Then, the first query returns those records with different values for RegionStaticMapID.

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