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[英]SQL Query to compare two columns with one column from another table (and get two values)
[英]Get frequency of data from two columns via one SQL query
我有桌子
_______________ | from | to | | 1 | 2 | | 2 | 2 | | 1 | 2 | | 3 | 2 |
当from
和to
是国家。
我需要获得前10名的国家遇到了from
和to
。
结果将是
________________ |country| count | | 2 | 5 | | 1 | 2 | | 3 | 1 |
我通过两个查询达到了所需的条件,但是我几乎可以肯定可以通过一个查询进行管理。
提前致谢。
您要使用UNION ALL
,然后使用GROUP BY
使用from和to的并集:
SELECT country, COUNT(*) AS count FROM
(SELECT from AS country FROM table_name
UNION ALL
SELECT to AS country FROM table_name)
GROUP BY country
ORDER BY count DESC
LIMIT 10
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