Internal Trigger to Obtain Newly Inserted Records - sql

Question

I am trying to execute a query but am having trouble. To start I have Table A and Table B. Table A has the following columns (RowID, ItemNumber, CaseCount, Elc, TotalElc, TimeStamp). Table B has the following columns( RowID, ItemNumber, Elc, TotalElc)
I am using a dashboard to insert values into Table A. I am inserting integers into ItemNumber, and CaseCount.
When these values are inserted, I am using an internal trigger on Table A after any inserts that have been made. The internal trigger obtains the values that were just inserted and uses the ItemNumber to lookup Table B to obtain the ELC and Totallc and insert it into Table A where the ItemNumber matches Table B.
How to obtain the values with the trigger to retrieve the newly inserted values (values being ItemNumber, CaseCount)?
Then after the values are retrieved, how to use the item numbers(will be 20 ItemNumbers inserted at once) to look up values in table B and insert them into Table A where the ItemNumber matches?
I don’t have much code since I am practically stuck on number one . Any help is most appreciated.
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER ObtainValues
ON Table A
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
-- Insert statements for trigger here
END
GO

Answer 1

As you have created Trigger on Table A, whenever a row is insert, SQL Server will create a table called INSERTED which holds newly added rows only. The scope of this INSERTED table is within your Trigger body only.
Check the below code:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER ObtainValues
ON Table A
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
UPDATE TableA
SET col1 = B.col1,
col1 = B.col1
FROM TableB B
WHERE B.ItemNumber = (SELECT ItemNumber FROM INSERTED)
END
GO
Similarly, when delete event occurs, DELETED table is created.

Answer 2

Taking Nithin's fine example as a starting point. I modified this so it will handle multiple row inserts.
CREATE TRIGGER ObtainValues
ON TableA
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
UPDATE TableA
SET col1 = B.col1,
col1 = B.col1
FROM TableB B
INNER JOIN TableA A on a.[YourPrimaryKey] = b.[YourPrimaryKey]
SET NOCOUNT OFF;
GO