Can a primary key have multiple rows?
4 Answers. You can’t (that’s the whole point of a primary key – you have one row per value). You need to split this into a couple of tables, one for visits and one for patients.
How do you select top 1 record in each group in SQL?
[dbo]. [InventoryAllocations] ORDER BY ROW_NUMBER() OVER(PARTITION BY DocumentID ORDER BY [RecordTimeStamp] DESC); TOP 1 works with WITH TIES here. WITH TIES means that when ORDER BY = 1 , then SELECT takes this record (because of TOP 1 ) and all others that have ORDER BY = 1 (because of WITH TIES ).
How to select first row from join return multple?
This is related to this question: Joining multiple tables results in duplicate rows I have two tables that I am joining. They share a key. The person table has one name per primary key but the email table has multiple emails per personId. I want to only show the first email per person.
How to join to first row in SQL Server?
In SQL Server 2005 and above, you could just replace INNER JOIN with CROSS APPLY: SELECT Orders.OrderNumber, LineItems2.Quantity, LineItems2.Description FROM Orders CROSS APPLY ( SELECT TOP 1 LineItems.Quantity, LineItems.Description FROM LineItems WHERE LineItems.OrderID = Orders.OrderID ) LineItems2
How does min work in MySQL left join only first row?
the condition that connects t1 and t2 is moved from the ON and into the inner query WHERE. the MIN (primary key) or LIMIT 1 makes sure that only 1 row is returned by the inner query. after selecting one specific row we need to tell the ON which row it is. that’s why the ON is comparing the primary key of the joined tabled.
Which is the first email in a join?
First email is literally the first email row per person. Edit 2: First email as I see it would be the first email row that shows up in the join as SQL works through the query. I does not matter which email shows up.