mysql group by，count一些用法

統計 一些信息以及每一個分組的個數    SELECT  a.name, a.phone, count(*) AS sum FROM xxx AS a GROUP BY a.order_id   統計 group by 以後的總條數（一共分了多少組）    SELECT COUNT(*) AS count_id FROM ( SELECT a.order_id FROM xxx group by

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