Merge Row values from different columns to one column on top of each other: MySQL

Question

I have Table1 with columns:

Fname,Sname

Table 2 with columns:

Fname,Lname

Now,in a query I want to take all the values from these two tables (First names and last names [Sname in table 1 is Lname]) and return to one columns. Basically I want to create column to get list of participants which include everyone from these two tables.
Is it possible?
Both the tables are joined indirectly via third table.

Answer 1

You can use UNION ALL will give all the rows from both tables.

SELECT 
  Fname,
  Sname,
  CONCAT(Fname,Sname) AS FSname
FROM table1
UNION ALL
SELECT 
  Fname,
  Lname,
  CONCAT(Fname,Lname) 
FROM table2;

The column names are taken from the first SELECT. If you use UNION and not UNION ALL rows in table2 which are duplicates of table1 will be omitted, but it can run slower as the values have to be compared.
You can use the third table and LEFT JOIN onto both tables and use COALESCE which returns the first argument which is not null.

SELECT 
COALESCE(t1.Fname,t2.Fname),
COALESCE(t1.Sname,t2.Lname),
CONCAT(
  COALESCE(t1.Fname,t2.Fname),
  COALESCE(t1.Sname,t2.Lname)
      ) AS FSname
FROM third_table t3
LEFT JOIN table1 t1
ON t1.id = t3.id
LEFT JOIN table2 t2 
ON t2.id = te.id;