sql 两个表字段叠加

要求：tableA表字段A与tableB表字段B叠加显示

代码：

select A as AB from tableA union all select distinct B from tableB;

添加条件：字段唯一显示

select distinct A as AB from tableA union all select distinct B from tableB;

添加条件：字段唯一显示，字段递减

select distinct A as AB from tableA union all select distinct B from tableB order by AB asc;

添加条件：字段唯一显示，字段递减，过滤重复

select distinct A as AB from tableA union select distinct B from tableB order by AB asc;