SQL：一个查询中有两个选择语句

Question

我想在一个查询中从两个 SQL 表中选择信息，但是这些信息是不相关的，所以不存在潜在的接头。

一个示例可能是以下设置。

tbl马德里

   id | name    | games | goals
    1 | ronaldo | 100   | 100
    2 | benzema | 50    | 25
    3 | bale    | 75    | 50
    4 | kroos   | 80    | 10

tbl巴塞罗那

   id | name    | games | goals
    1 | neymar  | 60    | 25
    2 | messi   | 150   | 200
    3 | suarez  | 80    | 80
    4 | iniesta | 40    | 5

我想要一个能提供以下信息的查询：

name    | games | goals
messi   | 150   | 200
ronaldo | 100   | 100

我试图遵循这个逻辑：Multiple select statements in Single query 但下面的代码不起作用：

USE Liga_BBVA

SELECT (SELECT name,
               games,
               goals
        FROM   tblMadrid
        WHERE  name = 'ronaldo') AS table_a,
       (SELECT name,
               games,
               goals
        FROM   tblBarcelona
        WHERE  name = 'messi')   AS table_b
ORDER  BY goals 

对这个有什么建议吗？谢谢 信息：足球的东西只是一个简化的例子。实际上，不可能将两个表合二为一并拥有一个新的“团队”列。这两个表有完全不同的结构，但我需要一些符合这个例子的特点。

Answer 1

你可以这样做：

 (SELECT
    name, games, goals
    FROM tblMadrid WHERE name = 'ronaldo')
 UNION
 (SELECT
    name, games, goals
    FROM tblBarcelona WHERE name = 'messi')
ORDER BY goals;

参见，例如：https://dev.mysql.com/doc/refman/5.0/en/union.html

Answer 2

如果您想将记录分开而不是合并。
试试下面的查询

SELECT (SELECT name,
               games,
               goals
        FROM   tblMadrid
        WHERE  name = 'ronaldo') AS table_a,
       (SELECT name,
               games,
               goals
        FROM   tblBarcelona
        WHERE  name = 'messi')   AS table_b
FROM DUAL

Answer 3

在这种情况下使用联合会有所帮助。

您还可以在始终返回 true 且与这些表中的数据无关的条件上使用连接。见下文

select tmd .name,tbc.goals from tblMadrid tmd join tblBarcelona tbc on 1=1;

Answer 4

select name, games, goals
from tblMadrid where name = 'ronaldo'
union
select name, games, goals
from tblBarcelona where name = 'messi'
ORDER  BY goals 

Answer 5

只要列匹配，您就可以合并查询。

SELECT name,
       games,
       goals
FROM   tblMadrid
WHERE  id = 1
UNION ALL
SELECT name,
       games,
       goals
FROM   tblBarcelona
WHERE  id = 2 

Answer 6

在这种情况下你可以使用 UNION

select id, name, games, goals from tblMadrid
union
select id, name, games, goals from tblBarcelona

你只需要在两个 SQL 中维护所选列的顺序，即 id、name、games、goals

Answer 7

UNION 语句是你的朋友：

SELECT   a.playername, a.games, a.goals
FROM     tblMadrid as a
WHERE    a.playername = "ronaldo"
UNION
SELECT   b.playername, b.games, b.goals
FROM     tblBarcelona as b
WHERE    b.playername = "messi"
ORDER BY goals;

Answer 8

您可以合并两个表中的数据，按目标最高的顺序排列，然后选择前两个，如下所示：

MySQL

select *
from (
  select * from tblMadrid
  union all
  select * from tblBarcelona
) alldata
order by goals desc
limit 0,2;

SQL 服务器

select top 2 *
from (
  select * from tblMadrid
  union all
  select * from tblBarcelona
) alldata
order by goals desc;

如果你只想要梅西和罗纳尔多

select * from tblBarcelona where name = 'messi'
union all
select * from tblMadrid where name = 'ronaldo'

要确保 messi 位于结果的顶部，您可以执行以下操作：

select * from (
  select * from tblBarcelona where name = 'messi'
  union all
  select * from tblMadrid where name = 'ronaldo'
) stars
order by name;