Using column variables in my WHERE clause - sql

Question

I have two tables (tableA and tableB) both with a name column. tableA's name column might be called NAME, tableB's column might be called FULLNAME, but they both are supposed to have the same value.
I am to write a query that pulls member id's (from either table) where these two column values are not the same. However, I'd like to pass the column names I'm checking via parameter, as this will be going in an SSRS report and in the future i'd like to be able to use it to compare any other column between these two tables.
Something like this:
DECLARE #COLUMN_A VARCHAR(50), #COLUMN_B VARCHAR(50)
/* COLUMN PARAMS WILL BE PASSED IN VIA SSRS */
SELECT
DISTINCT(MEMBER_ID)
FROM
TABLE_A
JOIN TABLE_B
ON (TABLE_A.MEMBER_ID = TABLE_B.MEMBER_ID)
WHERE
#COLUMN_A <> #COLUMN_B
Is something like this possible?
edit:
Or might something like this work?
DECLARE
#column VARCHAR(50)
SELECT #column = 'FIRST_NAME';
SELECT DISTINCT
MEMBR_ID,
case
when #column='FIRST_NAME' then MEMBR_FIRST_NAME
when #column='LAST_NAME' then MEMBR_LAST_NAME
end TABLE_1,
case
when #column='FIRST_NAME' then FIRSTNAME
when #column='LAST_NAME' then LASTNAME
end TABLE_2,
#column
FROM
TABLE_1
JOIN TABLE_2
ON (TABLE_1.MEMBR_ID = TABLE_2.MEMBR_ID)
WHERE
TABLE_1.#column <> TABLE_2.#column

Answer 1

Is something like this possible?
Technically, the syntax is fine. The where will be comparing two constant strings. The results will be either all rows or no rows, depending on whether the two strings are the same.
Do these evaluate to the columns? No, they do not. You cannot pass parameters into a SQL statement for identifiers -- column names, table names, schema names, database names, function names, or operators (for example).
You can do this using dynamic SQL, but you have to plug the names in:
DECLARE #sql NVARCHAR(MAX);
SET #sql = '
SELECT DISTINCT A.MEMBER_ID
FROM TABLE_A A JOIN
TABLE_B B
ON A.MEMBER_ID = B.MEMBER_ID
WHERE A.#COLUMN_A <> B.#COLUMN_B
';
SET #sql = REPLACE(#sql '#COLUMN_A', COLUMN_A);
SET #sql = REPLACE(#sql '#COLUMN_B', COLUMN_B);
exec sp_executesql #sql;