Understanding This FROM

[BootstrapperRI]

I'm having trouble understanding exactly what this FROM statement is doing. It's joining 'Tickets' with dfs where StoreID and EODID are the same, but it seems to be redundant with the Inner and Left joins? What are their separate purposes?

FROM
[DB].[dbo].[Tickets] AS t
	INNER JOIN [DB].[dbo].[DayfileSummary] AS dfs ON ( dfs.StoreID = t.StoreID ) AND ( dfs.EODID = t.EODID )
	LEFT JOIN [DB].[dbo].[Stores] ON dfs.StoreID = Stores.StoreID

TIA


David
MIS/IT Director

 

[fredericofonseca]

why do you think it is redundant?
its a perfectly valid join, with multi column on first join, single column on second join and basically telling us

give me all records that have an exact match between tickets and dayfilesummary and also any record from stores that may match the storeid.

where the "error" may exist is that you should never have a ticket or a dayfilesummary without a store, assuming that store is a parent for both tables.
but.... if this is a ETL that is loading data onto a DB maybe this sql is identifying records from an external source that do not yet have a storeid as a possible step to ignore records on the load.

Regards

Frederico Fonseca
SysSoft Integrated Ltd

http://www.syssoft-int.com

FAQ219-2884
FAQ181-2886