如何计算字符串语句

给定一个作为计算语句的字符串组合，我怎样才能得到结果，在本例中是下面代码中的列 cal 。 我知道我可以使用案例，但是有没有直接的方法来进行计算？

    create table tl_test
    (
            cl1 int
    )

    create table tl_test2
    (
            cl1 char(1)
    )
    insert into tl_test values (21), (43), (13), (36), (41)
    insert into tl_test2 values ( '+'), ('-'), ('*'), ('/')

    select *,
    cast(c1 as varchar) + f1 
    + cast(c2 as varchar) + f2 
    + cast(c3 as varchar) + f3 
    + cast(c4 as varchar) + f4 
    + cast(c5 as varchar) as cal
    from(
    SELECT A.cl1 as c1, f1.cl1 as f1,  b.cl1 as c2,f2.cl1 as f2, C.cl1 as c3, f3.cl1 as f3, D.cl1 as c4, f4.cl1 as f4,  E.cl1 as c5
    FROM TL_TEST A
    CROSS JOIN TL_TEST2 f1
    CROSS JOIN TL_TEST B
    CROSS JOIN TL_TEST2 f2
    CROSS JOIN TL_TEST C
    CROSS JOIN TL_TEST2 f3
    CROSS JOIN TL_TEST D
    CROSS JOIN TL_TEST2 f4
    CROSS JOIN TL_TEST E
    )a
    WHERE c1 != c2
    and c1 != c3
    and c1 != c4
    and c1 != c5
    and c2 != c3
    and c2 != c4 
    and c2 != c5
    and c3 != c4
    and c3 != c5
    and c4 != c5

您可以存储结果cal字符串中的列并使用EXEC https://msdn.microsoft.com/en-us/library/ms188332.aspx来计算你的答案。

DECLARE @sql NVARCHAR(MAX) = 'SELECT ' + (SELECT TOP 1 cal FROM result)
EXEC(@sql)