合并所有两个表但列数不同

select count(*) as total FROM ( SELECT * FROM database1.orders WHERE number LIKE "11111111111111111" UNION ALL SELECT * FROMdatabase2.orders WHERE number LIKE "11111111111111111" ) AS b

但我收到错误：

使用的 SELECT 语句具有不同的列数

因为跑SELECT * FROM database2.orders WHERE number LIKE "11111111111111111" 给我的结果为空。

如何将其与查询合并，因为用查询来帮助我处理分页

感谢您的帮助！

只需在之前进行聚合即可union all:

select sum(cnt) as total
FROM ((SELECT count(*) as cnt
       FROM database1.orders
       WHERE number LIKE '11111111111111111'
      )
      UNION ALL
      (SELECT count(*) as cnt
       FROM database2.orders
       WHERE number LIKE '11111111111111111'
      )
     ) t;

注意我将字符串分隔符更改为单引号而不是双引号。最好对字符串和日期常量使用单引号（仅此而已）。

顺便说一句，您还可以使用联接来执行此操作：

select o1.cnt1, o2.cnt1, (o1.cnt1 + o2.cnt1) as total
FROM (SELECT count(*) as cnt1
      FROM database1.orders
      WHERE number LIKE '11111111111111111'
     ) o1 cross join
     (SELECT count(*) as cnt2
      FROM database2.orders
      WHERE number LIKE '11111111111111111'
     ) o2;

这使得获取两个数据库的单独计数变得更加容易。