SQL bulk copy : Trigger not getting fired - sql

Question

I am copying data from Table1 to Table2 table using sql bulk copy. I have applied trigger on Table2, but my trigger is not firing on every row. Here is my trigger and sqlbulkcopy function.
SqlConnection dstConn = new SqlConnection(ConfigurationManager.ConnectionStrings["Destination"].ConnectionString);
string destination = dstConn.ConnectionString;
//Get data from Source in our case T1
DataTable dataTable = new Utility().GetTableData("Select * From [db_sfp_ems].[dbo].[tbl_current_data_new] where [start_date]>'" + calculate_daily_Time + "' and status=0" , source);
SqlBulkCopy bulkCopy = new SqlBulkCopy(source, SqlBulkCopyOptions.FireTriggers)
{
//Add table name of source
DestinationTableName = "tbl_current_data",
BatchSize = 100000,
BulkCopyTimeout = 360
};
bulkCopy.WriteToServer(dataTable);
//MessageBox.Show("Data Transfer Succesfull.");
dstConn.Close();
------Trigger-----
ALTER TRIGGER [dbo].[trgAfterInsert] ON [dbo].[tbl_current_data]
AFTER INSERT
AS
BEGIN
declare #intime datetime
declare #sdp_id numeric
declare #value numeric(9,2)
SELECT #intime= DATEADD(SECOND, -DATEPART(SECOND, start_date), start_date) FROM INSERTED
SELECT #sdp_id= sdp_id FROM INSERTED
SELECT #value= value FROM INSERTED
INSERT INTO Table3(sdp_id,value,start_date)
VALUES
(
#sdp_id,#value,#intime
)

Answer 1

A trigger is fired after an insert, whether that insert concerns 0, 1 or multiple records makes no difference to the trigger. So, even though you are inserting a whole bunch of records, the trigger is only fired once. This is by design, and not specific for BULK_INSERT; this is true for every kind of insert. This also means that the inserted pseudo table can hold 0, 1 or multiple records. This is a common pitfall. Be sure to write your trigger in such a way it can handle multiple records. For example: SELECT #sdp_id= sdp_id FROM INSERTED won't work as expected if inserted holds multiple records. The variable will be set, but you cannot know what value (from which inserted record) it's going to hold.
This is all part of the set based philosophy of SQL, it is best not to try and break that philosophy by using loops or other RBAR methods. Stay in the set mindset.

Answer 2

Your trigger is simply broken. In SQL Server, triggers handle multiple rows at one time. Assuming that inserted has one row is fatal error -- and I wish it caused a syntax error.
I think this is the code you want:
ALTER TRIGGER [dbo].[trgAfterInsert] ON [dbo].[tbl_current_data]
AFTER INSERT
AS
BEGIN
INSERT INTO Table3 (sdp_id, value, start_date)
SELECT sdp_id, value,
DATEADD(SECOND, -DATEPART(SECOND, start_date), start_date)
FROM inserted i;
END;
Apart from being correct, another advantage is that the code is simpler to write.
Note: You are setting the "seconds" part to 0. However -- depending on the type -- start_date could have fractional seconds that remain. If that is an issue, ask another question.