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Tip of the Day
Language: Visual Basic
Expertise: Beginner
Jun 18, 1999



Building the Right Environment to Support AI, Machine Learning and Deep Learning

SQL Trick to Join Multiple Select Statements

Don't overlook the UNION keyword in SQL as a way to simplify selections from multiple tables. For instance, to select the customer with the highest sales from three tables with basically the same layout, use the UNION keyword to allow your VB code to open only one resultset with the answer:
Private Function MaxCustSales() As Long
	Dim sSql as string

	sSql =		"select max(cust_sales) max_sales from " & _
				"sales.dbo.sales_east " & "UNION " & _
				"select max(cust_sales) max_sales from " & _
				"sales.dbo.sales_west " & _"UNION " & _
				"select max(cust_sales) max_sales from " & _
				"sales.dbo.sales_intl " & _
				"ORDER BY max_sales DESC"
Do this to open the resultset:
	If NOT IsNull(!max_sales) Then
			MaxCustSales = !max_sales
	End If

End Function
Joe Karbowski
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