I'm trying to do a left join on data views _Sent, EventDate but after I run the query I get about 5 times more records and I don't understand why. In my data extension I have 400.000 records and after I append the date I get 1.7 million records. This is a 3 stage campaign when customers request notification for products not in stock and the confirmation is the first step, thanking the customer for requesting an email, instock is when the product is back and they receive an email and discontinued is when the product is no longer available.
This is my query:
Select a.SubscriberKey, a.EmailAddress, a.Etype, b.EventDate from [DataExtension] a left join [_Sent] b on a.SubscriberKey = b.SubscriberKey