SQL Server : split column into table in a trigger - sql

Question

I have a table that looks something like this:
UserID Email
-----------------------------------
1 1_0#email.com;1_1#email.com
2 2_0#email.com;2_1#email.com
3 3_0#email.com;3_3#email.com
And I need to create a temp table that will look like this:
UserID Email
-----------------------------------
1 1_0#email.com
1 1_1#email.com
2 2_0#email.com
2 2_1#email.com
3 3_0#email.com
3 3_1#email.com
The temp table will be used in a update trigger and I was wondering if there is a more elegant approach than doing something like this:
-- Create temp table to hold the result table
CREATE TABLE #resultTable(
UserID int,
Email nvarchar(50)
)
-- Create temp table to help iterate through table
CREATE TABLE #tempTable(
ID int IDENTITY(1,1),
UserID int,
Email nvarchar(50)
)
-- Insert data from updated table into temp table
INSERT INTO #tempTable
SELECT [UserId], [Email]
FROM inserted
-- Iterate through temp table
DECLARE #count int = ##ROWCOUNT
DECLARE #index int = 1
WHILE (#index <= #count)
BEGIN
DECLARE #userID int
DECLARE #email nvarchar(50)
-- Get the user ID and email values
SELECT
#userID = [UserID], #email = [Email]
FROM #tempTable
WHERE [ID] = #index
-- Insert the parsed email address into the result table
INSERT INTO #resultTable([UserID], [Email])
SELECT #userID, [Data]
FROM myFunctionThatSplitsAColumnIntoATable(#email, ';')
SET #index = #index + 1
END
-- Do stuff with the result table

Answer 1

You'd better avoid iterative approaches when using T-SQL unless strictly necessary, specially inside triggers.
You can use the APPLY operator.
From MSDN:
The APPLY operator allows you to invoke a table-valued function for each row returned by an outer table expression of a query.
So, you can try to replace all your code with this:
INSERT INTO #resultTable(UserID, Email)
SELECT T1.UserID
,T2.Data
FROM updated T1
CROSS APPLY myFunctionThatSplitsAColumnIntoATable(T1.Email, ';') AS T2