SQL：按列别名排序

Question

当我运行此查询时：

SELECT 'A' as table_name, count() FROM A 
UNION ALL SELECT 'B' as table_name, count() FROM B
UNION ALL SELECT 'C' as table_name, count() FROM C ORDER BY table_name ASC;

输出为：

table_name  count
-----------------
B            0
C            0
A            0

它不是按table_name列排序的，我该如何对其排序并获得输出：

 table_name  count
 -----------------
  A            0
  B            0
  C            0

Answer 1

您可以尝试以下-

select * from
(
SELECT 'A' as table_name, count() FROM A 
UNION ALL 
SELECT 'B' as table_name, count() FROM B
UNION ALL 
SELECT 'C' as table_name, count() FROM C
)tbl ORDER BY table_name ASC