Question

我有一个SQLite表，其中有一个消息列表：

to  | from
==========
9999  ME
9999  ME
ME    9999
ME    8888

查询结果应采用以下格式：

数字（匹配的记录数）

9999 (3)
8888 (1)

如何编写查询以向我提供此结果集？我正在使用Android。

Answer 1

也许您可以使用此http://www.postgresql.org/docs/current/static/functions-conditional.html

执行某些操作

我想这样的事情（没有运行它）：

SELECT number, count(number) as `Count` FROM (
  SELECT 
    CASE
      WHEN to = 'ME' THEN from
      ELSE to
    END AS number
    FROM table
  ) GROUP BY number;

Answer 2

SELECT value, count(*)  
FROM ( 
   SELECT to as value
   FROM your_table

   UNION ALL

   SELECT "from" as value
   FROM your_table
) t
GROUP BY value

要过滤掉to和from的不需要的值，请使用适当的WHERE子句（理想情况是在内部选择中，以减少需要处理的行数。

Answer 3

select  value, sum (count) as count, from 
(
    select count(*) as count , "from" as value from your_table 
    group by "from"
   union all 
   select count(*) as count , "to" as value from your_table 
   group by "to" 
) t
group by t.value

谢谢@a_horse_with_no_name＆amp; @razvi！

Answer 4

如果您只想计算数值的出现次数，这应该有用。

使用连接（“||”）来形成所需的输出。

SELECT to_from || ' (' || count(to_from) || ')' FROM (
  SELECT
    CASE 
      WHEN to ~ '^[0-9]+$' THEN to
      WHEN from ~ '^[0-9]+$' THEN from
    END to_from
  FROM
    testing
) a
GROUP BY to_from

结果

 ?column? 
----------
 9999 (3)
 8888 (1)
(2 rows)

SQL查询以查找两列中的值计数

4 个答案: