Compare Identical Columns of 2 Different Table for Mismatch Data - sql-server

Question

I have the following query to check if usernames are the exact same between to tables
SELECT
--Username
a.username as 'TABLE_1_USERNAME',
b.username as 'TABLE_2_USERNAME',
CASE
WHEN a.username IS NULL AND b.username IS NULL THEN 'True'
WHEN a.username = b.username THEN 'True'
ELSE 'False'
END AS 'Is Equal?'
FROM User a
JOIN User_Group b ON a.id = b.id
This works great to tell me if usernames differ for any reason, but what I'd like to do is recursively compare each column between the User table and the User_Group Table (without having to write each one out) - both of the table's column names are identical. Is this possible in SQL Server?
Leaving out casing checks and trimming for brevity

Answer 1

Try this. Except shows any rows in the two queries that don't fully match
SELECT * FROM User_Group
EXCEPT
SELECT * FROM User

Answer 2

Here's a dynamic sql method for doing literally what you're asking for:
DECLARE #cols TABLE (id int identity(1,1), colname varchar(25))
INSERT INTO #cols (colname) select COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'User' AND COLUMN_NAME <> 'id'
declare #sql nvarchar(max)
select #sql = 'SELECT a.id, '
declare #maxval int
select #maxval = max(id) from #cols
declare #c int = 1
declare #curcol varchar(25)
while #c <= #maxval
begin
if #c > 1
select #sql += ', '
select #curcol = colname from #cols where id = #c
select #sql += 'a.' + #curcol + ' as ''Table_1_' + #curcol + ''', b.' + #curcol + ' as ''Table_2_' + #curcol + ''',
CASE
WHEN a.' + #curcol + ' IS NULL AND b.' + #curcol + ' IS NULL THEN ''True''
WHEN a.' + #curcol + ' = b.' + #curcol + ' THEN ''True''
ELSE ''False''
END AS ''Is Equal?'''
set #c = #c + 1
end
select #sql += 'FROM [User] a
INNER JOIN User_Group b ON a.id = b.id'
exec sp_executesql #sql
With the following test data:
create table [User] (id int, username varchar(10), fname varchar(25), lname varchar(25))
create table [User_Group] (id int, username varchar(10), fname varchar(25), lname varchar(25))
insert into [User] values (1, 'user1', 'fname1', 'lname1')
insert into [User_Group] values (1, 'user1', 'fname1', 'lname1')
insert into [User] values (2, 'user2', 'fname2', 'lname2')
insert into [User_Group] values (2, 'user2', 'fnameasdf', 'lnamesdfg')
It generates this output:
id Table_1_username Table_2_username Is Equal? Table_1_fname Table_2_fname Is Equal? Table_1_lname Table_2_lname Is Equal?
1 user1 user1 True fname1 fname1 True lname1 lname1 True
2 user2 user2 True fname2 fnameasdf False lname2 lnamesdfg False
Here's the query it generates:
SELECT a.id, a.username as 'Table_1_username', b.username as 'Table_2_username',
CASE
WHEN a.username IS NULL AND b.username IS NULL THEN 'True'
WHEN a.username = b.username THEN 'True'
ELSE 'False'
END AS 'Is Equal?', a.fname as 'Table_1_fname', b.fname as 'Table_2_fname',
CASE
WHEN a.fname IS NULL AND b.fname IS NULL THEN 'True'
WHEN a.fname = b.fname THEN 'True'
ELSE 'False'
END AS 'Is Equal?', a.lname as 'Table_1_lname', b.lname as 'Table_2_lname',
CASE
WHEN a.lname IS NULL AND b.lname IS NULL THEN 'True'
WHEN a.lname = b.lname THEN 'True'
ELSE 'False'
END AS 'Is Equal?'FROM [User] a
INNER JOIN User_Group b ON a.id = b.id