请教一个sql查询问题

因为你的类型是固定的，所以直接查询，如果你的类型不固定，可以参考上面的链接。

SELECT TT.Month

,SUM(CASE WHEN TT.TYPE = 'B' THEN Count ELSE 0 END) AS B
,SUM(CASE WHEN TT.TYPE = 'M' THEN Count ELSE 0 END) AS M
,SUM(CASE WHEN TT.TYPE = 'D' THEN Count ELSE 0 END) AS D
,SUM(CASE WHEN TT.TYPE = 'T' THEN Count ELSE 0 END) AS T

FROM (
SELECT TO_CHAR(T1.ACTIVATE_TIME, 'yyyy-MM') AS Month

    , T2.TYPE
    , COUNT(*) AS Count
  FROM TL_CSU_ACTIVATE_LOG T1
  LEFT JOIN TV_CSU_USER T2 ON T2.USER_ID = T1.USER_ID
  WHERE TO_CHAR(T1.ACTIVATE_TIME, 'yyyy-MM') >= '2014-12' AND TO_CHAR(T1.ACTIVATE_TIME, 'yyyy-MM') <= '2015-12'

GROUP BY T2.TYPE
) TT
GROUP BY TT.Month
ORDER BY TT.Month