Compare uniqueidentifier in where clause

问题

We have two tables : MainTable and CloneOfMainTable

The structure of both tables is :

ID : int Identity Primarykey
Foo: nvarchar(50) 
RowVersion : uniqueidentifier

We want to simply get the updated rows by comparing RowVersion and bla bla ...

SELECT * 
FROM MainTable 
INNER JOIN CloneOfMainTable On MainTable.ID = CloneOfMainTable.ID
WHERE MainTable.RowVersion <> CloneOfMainTable.RowVersion

and it doesn't work ^_^"

回答1:

There are no limitations on comparing uniqueidentifier values. As the column is nullable you may use coalesce to include null values in comparison:

WHERE coalesce(MainTable.RowVersion,'00000000-0000-0000-0000-000000000000') <> coalesce(CloneOfMainTable.RowVersion,'00000000-0000-0000-0000-000000000000')

来源：https://stackoverflow.com/questions/29731416/compare-uniqueidentifier-in-where-clause