SQL的字符转换问题

[Mapleleaf123]

CREATE VIEW t
AS
SELECT
a.a + a.b + a.c as tt from ttt as a

如果表ttt中的a,b,c为字符类型时就可以
现在出现的问题是a,b,c类型不同
应该如何处理？

[yrwx001]

CREATE VIEW t
AS
SELECT
cast(a.a as varchar(10)) + cast(a.b as varchar(10)) + cast(a.c as varchar(10)) as tt from ttt as a

[leo_lesley]

CREATE VIEW t
AS
SELECT isnull(a.a,'') + isnull(a.b,'') + isnull(a.c,'') as tt from ttt as a

[leo_lesley]

--刚刚看错了，用ls的吧，不过要改改，转换成varchar时最好不要加长度，不然长度超出了，就会截断了。
CREATE VIEW t
AS
SELECT
cast(a.a as varchar) + cast(a.b as varchar) + cast(a.c as varchar) as tt from ttt as a