T-SQL Merge Two Comma-Separated Columns - sql-server

Question

I'm trying to merge one table into another (we'll call them Stage and Prod) that controls users and their permissions. My end result should be a single Prod table that has combined each userid's permissions from Stage into Prod. The issue I'm having though is that the tables were designed by an outside vendor and contain multiple pieces of information in one comma-delimited column.
Stage might look like below:
Userid | Permissions
----------------------------------------------------------------
1 | schedule,upload,test,download,admin
2 | test,upload
3 | download
Prod:
Userid | Permissions
----------------------------------------------------------------
1 | test,admin,schedule,download,upload
2 | admin
3 | download,upload
When they're merged, the userids should have their permissions from Stage, combined with those in Prod. However, tackling this when the permissions are a comma-delimited string has me at wit's end.
In the final result below, userid 1's permissions remain unchanged because they are the same in Stage as they are in Prod, merely in a different order.
Userid 2 had his Stage permissions added to his Prod since he did not have those permissions yet.
Userid 3 had his Prod permissions unchanged since his Stage permissions are already included.
Result:
Userid | Permissions
----------------------------------------------------------------
1 | test,admin,schedule,download,upload
2 | admin,test,upload
3 | download,upload
Is there any way to do this? Hopefully this makes some sense, but if there's any more info that might help I'm happy to try to provide it. Thank you for any help at all.

Answer 1

Interestingly enough, this was a topic of discussion on a MSSQLTips blog by Aaron Bertrand. Borrowing his code you can create the Numbers table and string splitting/reassembling functions required to make the following work. If you are planning on doing this often and are stuck with the schema you've shown, this is the way to go.
/*Create Test Data
create table StagePermissions (UserID int, [Permissions] nvarchar(max));
create table ProdPermissions (UserID int, [Permissions] nvarchar(max));
insert StagePermissions values
(1,'schedule,upload,test,download,admin'),
(2,'test,upload'),
(3,'download')
insert ProdPermissions values
(1,'test,admin,schedule,download,upload'),
(2,'admin'),
(3,'download,upload')
*/
select sp.UserID, dbo.ReassembleString(sp.Permissions+','+pp.Permissions,',',N'OriginalOrder') MergedPermissions
from StagePermissions sp
join ProdPermissions pp on pp.UserID=sp.UserID

Answer 2

Taking Steve's test data, but adding:
create table BothPermissions (UserID int, [Permissions] nvarchar(max));
This code will work with a fixed number of possible permissions.
DECLARE #XPermissions TABLE (
UserID int
,XSchedule BIT
,XUpload BIT
,XTest BIT
,XDownload BIT
,XAdmin BIT
)
INSERT INTO #XPermissions
SELECT
ISNULL(sp.UserID,pp.UserID),
CHARINDEX('schedule',sp.[Permissions]) + CHARINDEX('schedule',pp.[Permissions]),
CHARINDEX('upload',sp.[Permissions]) + CHARINDEX('upload',pp.[Permissions]),
CHARINDEX('test',sp.[Permissions]) + CHARINDEX('test',pp.[Permissions]),
CHARINDEX('download',sp.[Permissions]) + CHARINDEX('download',pp.[Permissions]),
CHARINDEX('admin',sp.[Permissions]) + CHARINDEX('admin',pp.[Permissions])
FROM StagePermissions sp
FULL JOIN ProdPermissions pp
ON sp.UserID = pp.UserID
INSERT INTO BothPermissions
SELECT
UserID,
CASE XSchedule WHEN 0 THEN '' ELSE 'schedule ' END +
CASE XUpload WHEN 0 THEN '' ELSE 'upload ' END +
CASE XTest WHEN 0 THEN '' ELSE 'test ' END +
CASE XDownload WHEN 0 THEN '' ELSE 'download ' END +
CASE XAdmin WHEN 0 THEN '' ELSE 'admin' END
FROM #XPermissions
UPDATE BothPermissions
SET [Permissions] = REPLACE(RTRIM([Permissions]),' ',', ')
Now, I was further curious about Steve's answer. I think it is the most robust solution here. However, I wondered how it would perform with a large dataset. I still don't know the answer because I haven't set up the tools necessary to use it. But here's a query that includes some random number generation to populate 10,000 records of each:
SELECT GETDATE()
DECLARE #StagePerms TABLE (
UserID INT IDENTITY
,Perms NVARCHAR(MAX)
)
DECLARE #ProdPerms TABLE (
UserID INT IDENTITY
,Perms NVARCHAR(MAX)
)
DECLARE #Counter INT = 0
DECLARE #XString NVARCHAR(MAX)
WHILE #Counter < 10000
BEGIN
SET #Counter += 1
SET #XString = REPLACE(RTRIM(
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'test ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'admin ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'schedule ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'download ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'upload ' END)
,' ',', ')
INSERT INTO #StagePerms SELECT #XString
SET #XString = REPLACE(RTRIM(
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'test ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'admin ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'schedule ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'download ' END +
CASE ROUND(RAND()-.2,0) WHEN 0 THEN '' ELSE 'upload ' END)
,' ',', ')
INSERT INTO #ProdPerms SELECT #XString
END
SELECT GETDATE()
DECLARE #BothPerms TABLE (
UserID INT
,Perms NVARCHAR(MAX)
)
DECLARE #XPerms TABLE (
UserID int
,XSchedule BIT
,XUpload BIT
,XTest BIT
,XDownload BIT
,XAdmin BIT
)
INSERT INTO #XPerms
SELECT
ISNULL(sp.UserID,pp.UserID),
CHARINDEX('schedule',sp.Perms) + CHARINDEX('schedule',pp.Perms),
CHARINDEX('upload',sp.Perms) + CHARINDEX('upload',pp.Perms),
CHARINDEX('test',sp.Perms) + CHARINDEX('test',pp.Perms),
CHARINDEX('download',sp.Perms) + CHARINDEX('download',pp.Perms),
CHARINDEX('admin',sp.Perms) + CHARINDEX('admin',pp.Perms)
FROM #StagePerms sp
FULL JOIN #ProdPerms pp
ON sp.UserID = pp.UserID
INSERT INTO #BothPerms
SELECT
UserID,
CASE XTest WHEN 0 THEN '' ELSE 'test ' END +
CASE XAdmin WHEN 0 THEN '' ELSE 'admin ' END +
CASE XSchedule WHEN 0 THEN '' ELSE 'schedule ' END +
CASE XDownload WHEN 0 THEN '' ELSE 'download ' END +
CASE XUpload WHEN 0 THEN '' ELSE 'upload ' END
FROM #XPerms
UPDATE #BothPerms
SET Perms = REPLACE(RTRIM(Perms),' ',', ')
SELECT * FROM #BothPerms
SELECT GETDATE()
The random number generation took less than a second; the rest took about 31 seconds. Steve, I'd be interested to see a comparison. Doesn't matter, obviously, if the data doesn't allow for my solution. And I'm sure there's a sweet spot somewhere.

Answer 3

Please make use of the below query. Its working fine in SQL Server 2012.
DECLARE #Stage TABLE (Userid int, Permission Varchar (8000))
DECLARE #Prod TABLE (Userid int, Permission Varchar (8000))
DECLARE #temp TABLE (Userid int, Permission Varchar (8000))
INSERT #Stage
(Userid,Permission)
VALUES
(1,'schedule,upload,test,download,admin'),
(2,'test,upload'),
(3,'download')
INSERT #Prod
(Userid,Permission)
VALUES
(1,'test,admin,schedule,download,upload'),
(2,'admin'),
(3,'download,upload')
-- Execution Part
INSERT INTO #temp
(Userid,Permission)
(
SELECT A.Userid AS Userid,Split.a.value('.', 'VARCHAR(100)') AS Permission FROM
(SELECT Userid,CAST ('<M>' + REPLACE(Permission, ',', '</M><M>') + '</M>' AS XML) AS Permission FROM #Stage A) AS A
CROSS APPLY Permission.nodes ('/M') AS Split(a)
UNION
SELECT A.Userid AS Userid,Split.a.value('.', 'VARCHAR(100)') AS Permission FROM
(SELECT Userid,CAST ('<M>' + REPLACE(Permission, ',', '</M><M>') + '</M>' AS XML) AS Permission FROM #Prod A) AS A
CROSS APPLY Permission.nodes ('/M') AS Split(a)
)
SELECT Userid, Permission =
STUFF((SELECT ', ' + Permission
FROM #temp b
WHERE b.Userid = a.Userid
FOR XML PATH('')), 1, 2, '')
FROM #temp a
GROUP BY Userid
OUTPUT
Userid Permission
1 admin, download, schedule, test, upload
2 admin, test, upload
3 download, upload

Answer 4

You can also use direct support of string splitting introduced in SQL Serv 2016 (in case you started using this engine version already of course :) )
STRING_SPLIT returns single column table...