How to avoid NULL when using Value-Name Mapping in SQL - sql-server

Question

I have a table like the following which is basically used to "give a name" to a value in a table (this table contains values for a bunch of other tables as well, not just for MYTABLE; I've omitted a few irrelevant fields from NAMEVALUEMAP):
NAMEVALUEMAP Table
---------------------
VALUE_ | NAME_
---------------------
0 | ZERO
1 | ONE
I didn't want to use JOINs so I thought of using Sub-Queries.
Problem is when a value does not exist in the NAMEVALUEMAP table then NULL is shown.
Instead of NULL I want to show the actual value from MYTABLE (MYTABLE has ID field as identity column and contains a few rows):
-- //Fine, prints word 'ZERO' when MYTABLE.ABC is 0
SELECT
(SELECT NAME_ FROM NAMEVALUEMAP WHERE VALUE_ = (SELECT ABC FROM MYTABLE inner_ WHERE inner_.ID = outer_.ID))
FROM
MYTABLE outer_
-- //Not Fine, prints NULL (because "999" is not in NAMEVALUEMAP). In this case, MYTABLE.ABC is 999
-- //Want it to print 999 if the value is not in NAMEVALUEMAP
SELECT
(SELECT NAME_ FROM NAMEVALUEMAP WHERE VALUE_ = (SELECT ABC FROM MYTABLE inner_ WHERE inner_.ID = outer_.ID))
FROM
MYTABLE outer_
-- //Tried COALESCE, but the error is "Invalid column name 'VALUE_'"
SELECT
COALESCE((SELECT NAME_ FROM NAMEVALUEMAP WHERE VALUE_ = (SELECT ABC FROM MYTABLE inner_ WHERE inner_.ID = outer_.ID)), ABC)
FROM
MYTABLE outer_
Also, is there a better way to do this sort of value-to-name mapping?

Answer 1

I would recomend using a LEFT JOIN (is there any reason you are voidung it?) and ISNULL
SELECT ISNULL(NAME_, ABC)
FROM MYTABLE m LEFT JOIN
NAMEVALUEMAP n ON m.ABC = n.VALUE_
Well, in that case you can try
SELECT ISNULL((select NAME_ FROM NAMEVALUEMAP WHERE VALUE_ = m.ABC), m.ABC)
FROM MYTABLE m

Answer 2

It is a left join, unless you want soem EXISTS/UNION construct. Not tested:
SELECT
COALESCE(N.VALUE, M.ABC)
FROM
MYTABLE M
LEFT JOIN
NAMEVALUEMAP N ON M.VALUE N.ABC
If you really want to avoid JOINs...
SELECT
ABC
FROM
MYTABLE M
WHERE
NOT EXISTS (SELECT * FROM NAMEVALUEMAP N WHERE M.VALUE N.ABC)
UNION ALL
SELECT
VALUE
FROM
NAMEVALUEMAP N
WHERE
EXISTS (SELECT * FROM MYTABLE M WHERE M.VALUE N.ABC)
Edit:
The SELECT *, 1 or NULL in EXISTS question again
Try EXISTS (SELECT 1/0...)
Mentioned in ANSI SQL 1992 Standard too, page 191

Answer 3

EDIT:
SELECT
COALESCE(
(SELECT NAME_ FROM NAMEVALUEMAP WHERE VALUE_ =
(SELECT ABC FROM MYINNERTABLE inner_ WHERE inner_.ID = outer_.ID)
),
<int to string>(
SELECT ABC FROM MYINNERTABLE inner_ WHERE inner_.ID = outer_.ID
)
)
FROM
MYTABLE outer_
where column function <int to string> is appropriate for sqlserver. In mysql it would be CAST(). Without conversion, the query will throw a wobbly about the mismatched datatypes.