Mysql 在单个SELECT语句中获取每月数据分布

我需要使用一个mysql语句每月分发一次数据。下面语句的预期结果：一个包含12行的表。如果一个月内没有可用数据，则该月应返回0。但是，在当前SQL语句的结果中，如果缺少数据，则缺少一行或多行。我错过了什么

选择m.月作为m1，选择月（从\u UNIXTIME（crdate））作为m2，
求和（当keylock=1时为1，否则0结束）为c1，求和（当keylock=2时为1，否则0结束）为c2
从tx_bhm_域_模型_访问a
右外连接(
选择1作为月份
联合选择2作为月份
工会选择3作为月份
工会选择4作为月份
工会选择5作为月份
工会选择6作为月份
工会选择7作为月份
工会选择8作为月份
工会选择9作为月份
工会选择10作为月份
工会选择11作为月份
联合选择12作为月份）m
月日（自上次时间（a.crdate））=月日
其中，年份（自下一个时间（a.crdate））=2018年
按月分组
按月订购

需要在

ON

子句中进行

年（）比较。我更喜欢左连接

：

SELECT m.Month as m1, MONTH(FROM_UNIXTIME(crdate)) as m2,
       SUM(CASE WHEN keylock = 1 THEN 1 ELSE 0 END) AS c1,
       SUM(CASE WHEN keylock = 2 THEN 1 ELSE 0 END) AS c2
FROM (SELECT 1 AS Month UNION ALL
      SELECT 2 AS Month UNION ALL 
      SELECT 3 AS Month UNION ALL
      SELECT 4 AS Month UNION ALL 
      SELECT 5 AS Month UNION ALL
      SELECT 6 AS Month UNION ALL
      SELECT 7 AS Month UNION ALL
      SELECT 8 AS Month UNION ALL
      SELECT 9 AS Month UNION ALL
      SELECT 10 AS Month UNION ALL
      SELECT 11 AS Month UNION ALL
      SELECT 12 AS Month
     ) m LEFT JOIN
     tx_bhm_domain_model_access a
     ON MONTH(FROM_UNIXTIME(a.crdate)) = m.Month AND
        YEAR(FROM_UNIXTIME(a.crdate)) = 2018 
GROUP BY m.Month
ORDER BY m.Month;

我还将

UNION

s更改为

UNION ALL

s。无需产生删除重复项的开销。

需要在

ON

子句中进行

年（）比较。我更喜欢左连接

：

SELECT m.Month as m1, MONTH(FROM_UNIXTIME(crdate)) as m2,
       SUM(CASE WHEN keylock = 1 THEN 1 ELSE 0 END) AS c1,
       SUM(CASE WHEN keylock = 2 THEN 1 ELSE 0 END) AS c2
FROM (SELECT 1 AS Month UNION ALL
      SELECT 2 AS Month UNION ALL 
      SELECT 3 AS Month UNION ALL
      SELECT 4 AS Month UNION ALL 
      SELECT 5 AS Month UNION ALL
      SELECT 6 AS Month UNION ALL
      SELECT 7 AS Month UNION ALL
      SELECT 8 AS Month UNION ALL
      SELECT 9 AS Month UNION ALL
      SELECT 10 AS Month UNION ALL
      SELECT 11 AS Month UNION ALL
      SELECT 12 AS Month
     ) m LEFT JOIN
     tx_bhm_domain_model_access a
     ON MONTH(FROM_UNIXTIME(a.crdate)) = m.Month AND
        YEAR(FROM_UNIXTIME(a.crdate)) = 2018 
GROUP BY m.Month
ORDER BY m.Month;

---

我还将

UNION

s更改为

UNION ALL

s。无需承担删除重复项的开销。

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