Question

我有这样的多个查询：

select id,name from phonebook WHERE (name='') AND (Tag ='') AND Country= ''; 
select id,name from phonebook WHERE (name='') AND Country= '';
select id,name from phonebook WHERE (tag='') AND Country= '';

我想在一个查询中加入它们（按此顺序）。

EIDT

我想在每个查询中放置顺序（不是全部）：

select id,name from phonebook WHERE (name='') AND (Tag ='') AND Country= '' order by points;

所以在每个查询中获得更高分的人将是第一个

Answer 1

select id, name, case when name='' and Tag ='' then 'all_empty'
                      when name='' then 'name_empty'
                      when Tag ='' then 'tag_empty'
                 end as result
from phonebook 
WHERE Country= '' and (name='' or Tag ='')
order by result

Answer 2

如果您想加入多个查询的结果，或者如果您想要实现您的解决方案，您可能正在寻找工会，请继续上述答案（但需要注意订单）：

select id,name from phonebook WHERE (name='') AND (Tag ='') AND Country= '' UNION
select id,name from phonebook WHERE (name='') AND Country= '' UNION
select id,name from phonebook WHERE (tag='') AND Country= '';

正如 MatBailie 在评论中所建议的，如果您希望重复导致每个查询都保留，请使用UNION ALL代替UNION。

MatBailie ：UNION将搜索结果并删除重复项。 UNION ALL甚至没有做出这种尝试。在这种情况下，我们事先知道三个查询没有相同的结果，因此UNION ALL将删除一些冗余的CPU工作量。此外，UNION可能会导致排序发生变化（重复数据删除），而UNION ALL不会（在我曾经使用过的RDBMS上）。

对于您的订购，这里有两种口味

SELECT * FROM 
(
  select id,name from phonebook WHERE (name='') AND (Tag ='') AND Country= '' order by Points
) DUMMY_ALIAS1

UNION ALL

SELECT * FROM 
(
  select id,name from phonebook WHERE (name='') AND Country= '' order by Points
) DUMMY_ALIAS2

UNION ALL

SELECT * FROM
( 
  select id,name from phonebook WHERE (tag='') AND Country= '' order by Points
) DUMMY_ALIAS3

OR

select id,name, points from phonebook WHERE (name='') AND (Tag ='') AND Country= '' UNION
select id,name, points from phonebook WHERE (name='') AND Country= '' UNION
select id,name, points from phonebook WHERE (tag='') AND Country= '' order by Points;

在一个查询mysql中加入多个查询

2 个答案: