mysql - 合并多个相似查询

Question

我可以从多个简单的查询中获得结果，但我想将它们进一步合并为子查询。

所有子查询都将与此类似-

SELECT COUNT(count) AS acc1 FROM (SELECT COUNT(table.colname) AS count 
FROM tablename GROUP BY tablename.sumcol HAVING count=1) as access1

其他人也是

SELECT COUNT(count) AS acc2 FROM (SELECT COUNT(table.colname) AS count
 FROM tablename GROUP BY tablename.sumcol HAVING count=2) as access2

Answer 1

您可以使用 UNION ALL 在同一结果集中获得两个结果

  SELECT 'acc1' , COUNT(count) 
  FROM ( SELECT COUNT(table.colname) AS count 
      FROM tablename G
      ROUP BY tablename.sumcol 
      HAVING count=1)  access1

  UNION ALL

  SELECT 'acc2', COUNT(count) 
  FROM (SELECT COUNT(table.colname) AS count
      FROM tablename 
      GROUP BY tablename.sumcol 
      HAVING count=2)  access2

我添加了 'acc1' 和 'acc2' 文字值以获得更好的结果读取，但你可以避免它

如果您需要同一行上的两个结果，您可以使用交叉连接(笛卡尔积)

  SELECT COUNT(count) as count_acc1, T.count2
  FROM ( SELECT COUNT(table.colname) AS count1
      FROM tablename G
      GROUP BY tablename.sumcol 
      HAVING count=1)  access1

  CROSS JOIN (

  SELECT COUNT(count)  as count2
  FROM (SELECT COUNT(table.colname) AS count
      FROM tablename 
      GROUP BY tablename.sumcol 
      HAVING count=2)  access2 ) T