Using T-SQL to parse EDI records is probably not the best way to accomplish whatever it is you're doing. You would get more useful advice posting this question in a C# or BizTalk forum. I'd suggest using an EDI integration API like Mirth to extract only the columns you need and in the format you need to a flat text file, then bulk copy the text file into SQL Server.

http://www.mirthcorp.com/products/mirth-connect

http://blogs.msdn.com/b/biztalknotes/archive/2014/05/02/installing-hl7-accelerator-for-biztalk-server.aspx