Add SQL Text Fields

CREATE TABLE Foo (a int, b text)

--Table Foo has b as text data type.

INSERT INTO Foo VALUES (1,'qwe')
INSERT INTO Foo VALUES (1,'zxc')
INSERT INTO Foo VALUES (2,'123')
INSERT INTO Foo VALUES (2,'abc')



select 

coalesce(convert(varchar(8000),t1.b), '')+ coalesce(convert(varchar(8000),t2.b), '')
from foo t1 join foo t2
on t1.a=t2.a

and coalesce(convert(varchar(8000),t1.b), '')< coalesce(convert(varchar(8000),t2.b), '')