在单个CTE上运行多个SQL查询

Question

Use case: A database table tracks cars on a lot. Each car must be inspected every three months. When I pull a list of cars to inspect, I also want to update their [Status] to reflect that. This can be done by using a temp table, but a common table expression would execute faster and make more sense if it could be used this way.

Attempted solution:

WITH CTE AS (
    SELECT ID
    FROM [dbo].[CarInventory]
    WHERE <car requires inspection> )

SELECT ID
    FROM CTE;

UPDATE [dbo].[CarInventory]
    SET Status = 'Queued for inspection'
    WHERE ID IN (SELECT ID FROM CTE);

The SELECT statement would run but I cannot find a way to use the CTE in the subsequent UPDATE statement. Is there some way to perform the SELECT and UPDATE using a CTE so I don't have to create a temp table?

Thanks!

Answer 1

I don't get it. Why are you selecting the id s? Just do:

UPDATE ci
    SET Status = 'Queued for inspection'
    FROM [dbo].[CarInventory] ci;
    WHERE <car requires inspection> ;

If you want to return the id s that are affected, use an OUTPUT clause.

Answer 2

By Inner Joining the CTE with the table that you want to update you will only update those joined records.

WITH CTE AS 
    (
    SELECT ID
    FROM [dbo].[CarInventory]
    WHERE <car requires inspection>  
    )

UPDATE [dbo].[CarInventory]
    SET Status = 'Queued for inspection'
    OUTPut CTE.*
FROM [dbo].[CarInventory]
INNER JOIN CTE ON [dbo].[CarInventory].ID = cte.ID

Answer 3

You can use the output clause of the update statement to get the list after the update.

https://docs.microsoft.com/en-us/sql/t-sql/queries/output-clause-transact-sql?view=sql-server-2017

Answer 4

I was simply barking up the wrong tree by using CTE in the first place. Thank you for setting me straight! Also, sorry to leave you guessing on software; I was using SSMS.

Using the OUTPUT clause recommended by Joe and Ryan to update a table and also view the affected records worked.

UPDATE [dbo].[CarInventory]
SET Status = 'Queued for inspection'
OUTPUT Deleted.ID
WHERE <car requires inspection>

I briefly poked at the VIEW mechanic that jarlh suggested. It looks like a bit more work than OUTPUT for this instance but I'm inspired to learn all about it now.