Convert a query of views into a single query with derived tables - sql

Question

Is it possible to convert (as in get the query as text) a query that consists of a lot of views within views into a query that is just based on the original tables?
The obvious is to go through all the views and then do it manually but wondered whether or not there was a quicker way?

Answer 1

It's not pretty, and like #David Faber commented, not sure how practical this will be, but here goes...
There's a whole lot of assumptions that one has to make for this to work, like
All of the views start with SELECT. (no CTE's)
The view is not enclosed in [ ] when referenced in another view
View names don't have spaces in them
This version only goes 1 level deep, but it should be possible to resolve any additional views you find in the output in a similar fashion.
And probably some more I didn't think of
I'm using the sys tables, and not the newer schema information objects, simply because I know the sys table structure better.
Assuming the following view
CREATE VIEW VW_DUMMY
AS
SELECT c.Name as Company, g.Name as [Group], gu.UserId
FROM VW_Company c
JOIN VW_Group g ON c.Id = g.CompanyId
JOIN VW_GroupUser gu ON g.Id = gu.GroupId AND gu.CompanyId = c.Id
Here's what I did.
1) Grab the view definition from syscomments for VW_DUMMY.
2) Strip off the CREATE VIEW part
2) Grab a list of objects that VW_DUMMY depends on from sysdepends
3) Grab the view definition from syscomments for all the dependant objects.
4) Strip off the CREATE VIEW part
5) Replace the name of the 'depends' object in the original view with the
definition...
1)
DECLARE #SQL VARCHAR(MAX);
SET #SQL = REPLACE((
SELECT c.text AS [text()]
FROM syscomments c
WHERE c.id = OBJECT_ID('VW_DUMMY')
FOR XML PATH('')), '
', '');
2)
SET #SQL = SUBSTRING(#SQL, PATINDEX('%SELECT%', #SQL), LEN(#SQL))
3), 4) and 5)
SELECT #SQL = REPLACE(#SQL, ' ' + name + ' ', '(' + SUBSTRING(text, PATINDEX('%SELECT%', text), LEN(text)) + ') ')
FROM (
SELECT DISTINCT OBJECT_NAME(depid) as name,
REPLACE((
SELECT c.text AS [text()]
FROM syscomments c
WHERE c.id = d.depid
FOR XML PATH('')), '
', '') as text
FROM sysdepends d
WHERE d.id = OBJECT_ID('VW_DUMMY')
AND exists(select 1 from sysobjects c where c.id = d.depid and c.type='V')) data
SELECT #SQL
I tried in on VW_DUMMY in my database, and the output is some of the worst formatted code that you might ever see, but the result is the same as the view.
Here's the output (bad formatting is deliberate)
SELECT c.Name as Company, g.Name as [Group], gu.UserId
FROM(SELECT *
FROM Company
) c
JOIN(SELECT *
FROM [Group]
) g ON c.Id = g.CompanyId
JOIN(SELECT *
FROM [GroupUser]
) gu ON g.Id = gu.GroupId AND gu.CompanyId = c.Id
Does that help?