我想加入两个select语句。它们各自都工作得很好，但如果我尝试使用union all，就会出现语法错误：
[42000][1064]您的sql语法有错误；请查看与mysql服务器版本对应的手册，以获取第29行“”附近要使用的正确语法
这对我来说毫无意义。我搜索了那个错误消息，但在那一行中没有使用引号（29是union all）

SELECT NULL                                                        AS id,
       table_a.calendar_day                             AS
       calendar_day,
       'XXX'                                                       AS mbr_entity
       ,
       'total'                                                    AS
       product,
       'total'                                                    AS
       mbr_stock_category,
       'total'                                                    AS component,
       SUM(IF(table_a.mbr_entity = 'XXX', aim, 0))      AS aim,
       SUM(IF(table_a.mbr_entity = 'XXX', cf, 0))       AS cf,
       SUM(IF(table_a.mbr_entity = 'XXX', mbr, 0))      AS mbr,
       SUM(IF(table_a.mbr_entity = 'XXX', ytd, 0))      AS ytd,
       SUM(IF(table_a.mbr_entity = 'XXX', forecast, 0)) AS forecast,
       SUM(table_b.a
           + table_b.b
           + table_b.c
           + table_b.d
           + table_b.e)                    AS actual
FROM   table_a
       left join table_b
              ON table_b.calendar_day =
                 table_a.calendar_day
                 AND table_b.mbr_entity =
                     table_a.mbr_entity
WHERE MONTH(table_a.calendar_day) = MONTH(CURRENT_DATE())
GROUP  BY calendar_day
UNION ALL
SELECT NULL                                                        AS id,
       table_a.calendar_day,
       table_a.mbr_entity,
       'total'                                                    AS product,
       'total'                                                    AS
       mbr_stock_category,
       'total'                                                    AS component,
       SUM(IF(table_a.mbr_entity = 'XXX', 0, aim))      AS aim,
       SUM(IF(table_a.mbr_entity = 'XXX', 0, cf))       AS cf,
       SUM(IF(table_a.mbr_entity = 'XXX', 0, mbr))      AS mbr,
       SUM(IF(table_a.mbr_entity = 'XXX', 0, ytd))      AS ytd,
       SUM(IF(table_a.mbr_entity = 'XXX', 0, forecast)) AS forecast,
       SUM(table_b.a
           + table_b.b
           + table_b.c
           + table_b.d
           + table_b.e)                    AS actual
FROM   table_a
       left join table_b
              ON table_b.calendar_day =
                 table_a.calendar_day
                 AND table_b.mbr_entity =
                     table_a.mbr_entity
WHERE  table_a.mbr_entity <> 'XXX'
AND MONTH(table_a.calendar_day) = MONTH(CURRENT_DATE())
GROUP  BY calendar_day,
          mbr_entity