Bulk Record Update with SQL
Your way is correct, and here is another way you can do it:
update Table1
set Description = t2.Description
from Table1 t1
inner join Table2 t2
on t1.DescriptionID = t2.ID
The nested select is the long way of just doing a join.
You can do this through a regular UPDATE
with a JOIN
UPDATE T1
SET Description = T2.Description
FROM Table1 T1
JOIN Table2 T2
ON T2.ID = T1.DescriptionId
Your approach is OK
Maybe slightly clearer (to me anyway!)
UPDATE
T1
SET
[Description] = t2.[Description]
FROM
Table1 T1
JOIN
[Table2] t2 ON t2.[ID] = t1.DescriptionID
Both this and your query should run the same performance wise because it is the same query, just laid out differently.