Every great god meets the novice don't know how to solve a problem, trouble to help have a look at the last question, thank!

CodePudding user response:

Can use condition exists, also can be associated with

 select count (1) the from (
Select distinct firs. Buyer_id from table1 as firs -- the first day 
Where the exists (
Select the from 1 
Table1 as SEC - the second day 
Where DATEDIFF (DAY, firs, SEC)=1 
And firs. Buyer_id=SEC. Buyer_id 
And firs. Item_id & lt;> The SEC. Item_id -- -- the first and second day buy goods different 
And the exists (
Select the from 1 
Table1 as tree - the third day 
Where DATEDIFF (DAY, firs. Buy_date, tree. Buy_date)=2 
And firs. Buyer_id=tree. Buyer_id 
And firs. Item_id & lt;> Tree. Item_id -- -- the first day and on the third day buy goods different 
)) as a