SQL数据库表查询分组问题，

Question

现在加入一个条件，根据WID查看当WID等于不同值时每个月的数量。。想实现当WID加入，也一样显示12个月的数据，没有数量的Num显示为0，求助SQL语句如何优化 ，最好帮打出来。

Answer 1

文本都不给！字段、表达式自己补完整。

;WITH a(wid) AS ( -- 所有 wid
    SELECT wid
      FROM wx_useropenid
     WHERE year(time_format) = 2016
  GROUP BY wid
),
b(month) AS ( -- 所有月份
    SELECT number
      FROM master..spt_values
     WHERE type = 'p'
       AND number BETWEEN 1 AND 12
)
-- (wid,月份) 作为统计主键
    SELECT NEWID() AS id,
           a.wid,
           b.month,
           ISNULL(count(w.id),0) AS num
      FROM a
      JOIN b
        ON 1=1
 LEFT JOIN wx_useropenid w
        ON a.wid = w.wid
       AND b.month = MONTH(b.time_format)
  GROUP BY a.wid, b.month