[每日一题] OCP1z0-047 :2013-08-20   GROUP BY扩展――GROUPING、ROLLUP.....................88

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正确答案：BD

在Oracle 8i中引入GROUPING(<列引用>)函数，被用来做为GROUPING()函数参数的表达式必须与出现在GROUPBY 子句中的表达式相匹配。包含了CUBE、ROLLUP或GROUPING SET关键字的组查询时，该函数对<列引用>相关列的聚合结果中的NULL值进行检查。例如通过写出decode(grouping(id),1,’ALLID’,id) id来检测id是否有一行由ROLLUP产生的空值，或着是否其在数据库中本身就是空值。如果这些NULL值是由本次ROLLUP查询生成的，那么返回1，否则返回0.

ROLLUP,该分组操作将生成一个结果集，此结果集除了包含正常分组之外，还包含小计(subtotal row)。ROLLUP操作字，对group by子句的各字段从右到左进行再聚合，逐个减少字段典型的总计和子计。如果是ROLLUP(A, B, C)的话，首先会对(A、B、C)进行GROUP BY，然后对(A、B)进行GROUP BY，然后是(A)进行GROUP BY，最后对全表进行GROUP BY操作（即GROUP BY()）
rollup(a,b,c)
相当于
group by a,b,c union all
group by a,b union all
group by a union all
group by ()

根据题意，执行以上ＳＱＬ返回如下结果：

hr@MYDB> SELECT e.department_id,e.job_id,d.location_id,sum(e.salary) total,   2  GROUPING(e.department_id)  GRP_DEPT,   3  GROUPING(e.job_id) GRP_JOB,   4  GROUPING(d.location_id)  GRP_LOC   5  FROM employees e JOIN departments d   6  ON e.department_id=d.department_id   7  GROUP BY ROLLUP(e.department_id,e.job_id,d.location_id);  DEPARTMENT_ID JOB_ID     LOCATION_ID      TOTAL   GRP_DEPT    GRP_JOB    GRP_LOC ------------- ---------- ----------- ---------- ---------- ---------- ----------            10 AD_ASST           1700       4400          0          0          0            10 AD_ASST                      4400          0          0          1            10                              4400          0          1          1            20 MK_MAN            1800      13000          0          0          0            20 MK_MAN                      13000          0          0          1            20 MK_REP            1800       6000          0          0          0            20 MK_REP                       6000          0          0          1            20                             19000          0          1          1            30 PU_MAN            1700      11000          0          0          0            30 PU_MAN                      11000          0          0          1            30 PU_CLERK          1700      13900          0          0          0            30 PU_CLERK                    13900          0          0          1            30                             24900          0          1          1            40 HR_REP            2400       6500          0          0          0            40 HR_REP                       6500          0          0          1            40                              6500          0          1          1            50 ST_MAN            1500      36400          0          0          0            50 ST_MAN                      36400          0          0          1            50 SH_CLERK          1500      64300          0          0          0            50 SH_CLERK                    64300          0          0          1            50 ST_CLERK          1500      55700          0          0          0            50 ST_CLERK                    55700          0          0          1            50                            156400          0          1          1            60 IT_PROG           1400      28800          0          0          0            60 IT_PROG                     28800          0          0          1            60                             28800          0          1          1            70 PR_REP            2700      10000          0          0          0            70 PR_REP                      10000          0          0          1            70                             10000          0          1          1            80 SA_MAN            2500      61000          0          0          0            80 SA_MAN                      61000          0          0          1            80 SA_REP            2500     243500          0          0          0            80 SA_REP                     243500          0          0          1            80                            304500          0          1          1            90 AD_VP             1700      34000          0          0          0            90 AD_VP                       34000          0          0          1            90 AD_PRES           1700      24000          0          0          0            90 AD_PRES                     24000          0          0          1            90                             58000          0          1          1           100 FI_MGR            1700      12008          0          0          0           100 FI_MGR                      12008          0          0          1           100 FI_ACCOUNT        1700      39600          0          0          0           100 FI_ACCOUNT                  39600          0          0          1           100                             51608          0          1          1           110 AC_MGR            1700      12008          0          0          0           110 AC_MGR                      12008          0          0          1           110 AC_ACCOUNT        1700       8300          0          0          0           110 AC_ACCOUNT                   8300          0          0          1           110                             20308          0          1          1                                          684416          1          1          1  50 rows selected.

把上面的SQL改写成如下这条ＳＱＬ，结果一样：

hr@MYDB> SELECT e.department_id,e.job_id,d.location_id,sum(e.salary) total,   2  GROUPING(e.department_id)  GRP_DEPT,   3  GROUPING(e.job_id) GRP_JOB,   4  GROUPING(d.location_id)  GRP_LOC   5  FROM employees e JOIN departments d   6  ON e.department_id=d.department_id   7  GROUP BY e.department_id,e.job_id,d.location_id   8  UNION ALL   9  SELECT e.department_id,e.job_id,null location_id,sum(e.salary) total,  10  GROUPING(e.department_id)  GRP_DEPT,  11  GROUPING(e.job_id) GRP_JOB,  12  1  GRP_LOC  13  FROM employees e JOIN departments d  14  ON e.department_id=d.department_id  15  GROUP BY e.department_id,e.job_id  16  UNION ALL  17  SELECT e.department_id,null job_id,null location_id,sum(e.salary) total,  18  GROUPING(e.department_id)  GRP_DEPT,  19  1 GRP_JOB,  20  1  GRP_LOC  21  FROM employees e JOIN departments d  22  ON e.department_id=d.department_id  23  GROUP BY e.department_id  24  UNION ALL  25  SELECT null department_id,null job_id,null location_id,sum(e.salary) total,  26  1 GRP_DEPT,  27  1 GRP_JOB,  28  1  GRP_LOC  29  FROM employees e JOIN departments d  30  ON e.department_id=d.department_id  31  order by 1,2;  DEPARTMENT_ID JOB_ID     LOCATION_ID      TOTAL   GRP_DEPT    GRP_JOB    GRP_LOC ------------- ---------- ----------- ---------- ---------- ---------- ----------            10 AD_ASST           1700       4400          0          0          0            10 AD_ASST                      4400          0          0          1            10                              4400          0          1          1            20 MK_MAN            1800      13000          0          0          0            20 MK_MAN                      13000          0          0          1            20 MK_REP                       6000          0          0          1            20 MK_REP            1800       6000          0          0          0            20                             19000          0          1          1            30 PU_CLERK          1700      13900          0          0          0            30 PU_CLERK                    13900          0          0          1            30 PU_MAN                      11000          0          0          1            30 PU_MAN            1700      11000          0          0          0            30                             24900          0          1          1            40 HR_REP                       6500          0          0          1            40 HR_REP            2400       6500          0          0          0            40                              6500          0          1          1            50 SH_CLERK                    64300          0          0          1            50 SH_CLERK          1500      64300          0          0          0            50 ST_CLERK                    55700          0          0          1            50 ST_CLERK          1500      55700          0          0          0            50 ST_MAN            1500      36400          0          0          0            50 ST_MAN                      36400          0          0          1            50                            156400          0          1          1            60 IT_PROG           1400      28800          0          0          0            60 IT_PROG                     28800          0          0          1            60                             28800          0          1          1            70 PR_REP            2700      10000          0          0          0            70 PR_REP                      10000          0          0          1            70                             10000          0          1          1            80 SA_MAN            2500      61000          0          0          0            80 SA_MAN                      61000          0          0          1            80 SA_REP            2500     243500          0          0          0            80 SA_REP                     243500          0          0          1            80                            304500          0          1          1            90 AD_PRES                     24000          0          0          1            90 AD_PRES           1700      24000          0          0          0            90 AD_VP             1700      34000          0          0          0            90 AD_VP                       34000          0          0          1            90                             58000          0          1          1           100 FI_ACCOUNT                  39600          0          0          1           100 FI_ACCOUNT        1700      39600          0          0          0           100 FI_MGR            1700      12008          0          0          0           100 FI_MGR                      12008          0          0          1           100                             51608          0          1          1           110 AC_ACCOUNT        1700       8300          0          0          0           110 AC_ACCOUNT                   8300          0          0          1           110 AC_MGR            1700      12008          0          0          0           110 AC_MGR                      12008          0          0          1           110                             20308          0          1          1                                          684416          1          1          1  50 rows selected.

哈哈。。。不知道大家有没有看出来，我就不再解释了！有问题大家可以上ITPUB找我：http://www.itpub.net/thread-1810748-1-1.html

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