C#直接执行SQL与查询SQL Server视图的性能差异对比

Great question—this is one of those common myths that trips up a lot of developers, so let's unpack it clearly.

核心结论：普通视图和直接写SQL性能完全一致 #

For your specific example with VeryComplexView (a standard non-indexed view), there is zero performance difference between querying the view in C# with:

new SqlCommand("SELECT * FROM VeryComplexView", connection)

and directly embedding the full SQL:

var query = @"SELECT e.ID, e.etc, s.etc FROM TableE AS e LEFT OUTER JOIN TableS AS s ON e.ID = s.NIP WHERE ID > 1000";
new SqlCommand(query, connection)

Why is that? #

SQL Server treats standard views as nothing more than stored SQL templates. When you run SELECT * FROM VeryComplexView, the database engine immediately "expands" the view's definition into the full underlying query, then runs the exact same query optimization process it would for the raw SQL you wrote in C#. The execution plan generated will be identical in both cases—no shortcuts, no pre-compiled magic here.

When would a view perform differently? #

The only exception is if you create an indexed view (also called a materialized view). To make one, you need to:

• Define the view with WITH SCHEMABINDING (locks the underlying table schema to prevent breaking changes)
• Create a clustered index on the view

Indexed views physically store the result set on disk, like a pre-computed table. This can speed up read-heavy queries, especially if the underlying join/filter logic is expensive to compute every time. But this comes with tradeoffs: writes to the underlying tables (TableE/TableS) will be slower because SQL Server has to update the indexed view's stored data too. For your example, since you're using a standard view, this doesn't apply.

So why use views at all? #

Views shine for maintainability and security, not raw performance:

• If 10 different parts of your app need this exact query, you can update the view's definition once instead of hunting down every instance of the raw SQL in your C# code.
• You can grant users permission to query the view without giving them direct access to the underlying TableE and TableS—great for limiting data exposure.

内容的提问来源于stack exchange，提问作者SIRS