Adding an additional column to SQL UNION SELECT - sql

Question

Suppose I have the following mapped and normalized tables;
Group User Contact BelongsTo
+-------+------+------+ +-------+------+------+ +-------+------+------+ +-------+------+
| gID| name| col3| | uID| fname| sname| | cID| name| col3| | accID| gID|
+-------+------+------+ +-------+------+------+ +-------+------+------+ +-------+------+
|1 |ABC |? | |1 |JJ |BB | |4 |ABCD |? | |1 |2 |
+-------+------+------+ +-------+------+------+ +-------+------+------+ +-------+------+
|2 |BCD |? | |2 |CC |LL | |5 |BCDE |? | |3 |2 |
+-------+------+------+ +-------+------+------+ +-------+------+------+ +-------+------+
|3 |DEF |? | |3 |RR |NN | |6 |CDEF |? | |5 |3 |
+-------+------+------+ +-------+------+------+ +-------+------+------+ +-------+------+
Using EERM, User and Contact are subclasses of "Account" superclass. (not shown) An account can belong to many groups, thus "BelongsTo" table records the M:N relationship between the Accounts and Group membership.
I would like an SQL statement which will allow me to query all the users and contacts that have membership in a Group matching conditions as follows:
SELECT
tc."cID" AS "accID",
tc."name" AS "accName",
tbt."gID"
FROM "tblContact" tc
INNER JOIN "tblBelongsTo" tbt
ON tbt."accID" = tc."cID"
UNION SELECT
tu."uID" AS "accID",
CONCAT (tu."fname", ' ', tu."sname") AS "accName",
tbt."gID"
FROM "tblUser" tu
INNER JOIN "tblBelongsTo" tbt
ON tbt."accID" = tu."uID"
ORDER BY "accID" ASC;
The above works, I have combined UNION SELECT in the query as the number of columns match either side when I CONCAT the forename and surname together. Resulting in a global "account_name" & "account_id" column.
My question is this: How would I go about adding an extra column so that I can see what the group name is?
ie from this:
Result
+-------+-------+------+
| accID|accName| gID|
+-------+-------+------+
|1 |JJBB |2 |
+-------+-------+------+
|3 |RRNN |2 |
+-------+-------+------+
|5 |BCDE |3 |
+-------+-------+------+
to this:
Result (2)
+-------+-------+------+------+
| accID|accName| gID| name|
+-------+-------+------+------+
|1 |JJBB |2 | BCD|
+-------+-------+------+------+
|3 |RRNN |2 | BCD|
+-------+-------+------+------+
|5 |BCDE |3 | DEF|
+-------+-------+------+------+
It seems everything I have tried causes the UNION SELECT to break (because of unmatched column). Likewise, I had little luck in combining sub-queries. I am probably missing something very obvious...
Thanks in advance.

Answer 1

You can join it to the group table to get the name.
select x.*, g.name
from group g join
(
SELECT
tc."cID" AS "accID",
tc."name" AS "accName",
tbt."gID"
FROM "tblContact" tc
INNER JOIN "tblBelongsTo" tbt
ON tbt."accID" = tc."cID"
UNION
SELECT
tu."uID" AS "accID",
CONCAT (tu."fname", ' ', tu."sname") AS "accName",
tbt."gID"
FROM "tblUser" tu
INNER JOIN "tblBelongsTo" tbt
ON tbt."accID" = tu."uID"
) x on x.gid = g.gid
order by accid;