Left Join, Union Select with multiple columns

Question

I have three tables with same-named columns, I want to select users distinctly from these all tables (no repeat) here is my query and it works,

SELECT User FROM Table1 UNION SELECT User FROM Table2 UNION SELECT User FROM Table3

How do I add another column to Select

something like this,

SELECT User, Time

But I only need to union on User column, Time column just for view purpose only.

Update: Here are the 3 tables I have. I want to get user names from these tables without repeating (distinct). and I want the time column to show in result

User  | Time     
Sam   | 12.00      
Jack  | 12.00      
Harry | 12.00      
John  | 12.00    
John  | 12.00    
Sam   | 12.00   

User    | Time     
Jacob   | 12.00      
Jack    | 12.00      
Harry   | 12.00      
John    | 12.00    
Charlie | 12.00    
Sam     | 12.00   

User    | Time     
Mason   | 12.00      
William | 12.00      
Harry   | 12.00      
John    | 12.00    
Charlie | 12.00    
Sam     | 12.00   

The result should be like this:

User    | Time     
Mason   | 12.00      
William | 12.00      
Harry   | 12.00      
John    | 12.00    
Charlie | 12.00    
Sam     | 12.00 
Jacob   | 12.00 
Jack    | 12.00

Answer 1

Since it sounds like your actual data, unlike your sample, has different timestamps for each user in the different tables, and you don't care which of those timestamps is picked as long as the user names are unique...

SELECT User, min(Time)
FROM (SELECT User, Time FROM Table1
      UNION ALL
      SELECT User, Time FROM Table2
      UNION ALL
      SELECT User, Time FROM Table3)
GROUP BY User;

Answer 2

Your sample data implies that the Time value is always the same, and therefore you don't mind picking any value in the table. One option here would be to just select a constant value as the Time value:

SELECT User, '12.00' AS Time FROM Table1 UNION ALL
SELECT User, '12.00' FROM Table2 UNION ALL
SELECT User, '12.00' FROM Table3