For the following query:
select item from (
select item from (select a as item from t1) tt
union all
select item from (select a as item from t1) tt
) ttt;
There is an if predicate in buildSimpleColFromDerivedTable() that compares
the outermost query field name (ttt.item) to the returned column list of
the inner query (tt.item) when building the returned column list of the
outer most query. In the above query example, the inner query field name
is an alias set in the inner most query and is set to "`tt`.`item`",
while the outermost query field name is set to "item". The use of
backticks "`" in the inner query alias is causing the execution to
not enter the if block which creates the SimpleColumn for the outermost
query field name. As a fix, we strip off the backticks from the inner
query alias.
