無法聯合所有兩個等效查詢？

Question

我有我需要重複幾次工作查詢，但是我對UNION越來越語法錯誤ALL：

工作查詢：

set @num := 0, @group := ''; 

select person, `group`, age 
from 
(
    select person, `group`, age, 
     @num := if(@group = `group`, @num + 1, 1) as row_number, 
     @group := `group` as dummy 
    from mytable 
    order by `Group`, Age desc 
) as x where x.row_number <= 2; 

SQL FIDDLE

失敗UNION ALL（獲取語法錯誤）：

set @num := 0, @group := ''; 
(
select person, `group`, age 
from 
(
    select person, `group`, age, 
     @num := if(@group = `group`, @num + 1, 1) as row_number, 
     @group := `group` as dummy 
    from mytable 
    order by `Group`, Age desc 
) as x where x.row_number <= 2; 
) 
UNION ALL 
(
select person, `group`, age 
from 
(
    select person, `group`, age, 
     @num := if(@group = `group`, @num + 1, 1) as row_number, 
     @group := `group` as dummy 
    from mytable 
    order by `Group`, Age desc 
) as x where x.row_number <= 2; 
) 

SQL FIDDLE

（在被聯合查詢只是出於測試目的，原始查詢的副本）

Answer 1

你有一些額外的支架。

看到這個SQL Fiddle

Answer 2

set @num := 0, @group := ''; 

select person, `group`, age 
from 
(
    select person, `group`, age, 
     @num := if(@group = `group`, @num + 1, 1) as row_number, 
     @group := `group` as dummy 
    from mytable 
    order by `Group`, Age desc 
) as x where x.row_number <= 2 
UNION ALL 

select person, `group`, age 
from 
(
    select person, `group`, age, 
     @num := if(@group = `group`, @num + 1, 1) as row_number, 
     @group := `group` as dummy 
    from mytable 
    order by `Group`, Age desc 
) as x where x.row_number <= 2; 

Answer 3

取出最外面的括號。 SELECT語句應該以SELECT關鍵字開始，而不是開放的paren。