聚合函数扫描一组记录，然后返回单行记录。这组记录可以是一个表或者视图、或者一个子查询的结果。OceanBase 支持的聚合函数详情请参考《OceanBase SQL参考（Oracle模式）》。

    聚合函数通常跟 GROUP BY 子句一起使用，按照一个或多个列的值分组，然后每组返回单笔记录。

    示例：分组统计每个仓库的销售额

    Oracle 租户中，聚合函数跟 GROUP BY 子句一起使用时，select_list 中需要严格包含 GROUP BY 后面的列；否则会报错。SQL查询如下：

    1. SELECT ol_w_id
    2.     , count(*) order_count
    3.     , sum(ol_amount)            sum_amount
    4.     , round(avg(ol_amount),2)   avg_amount
    5.     , min(ol_amount)            min_amount
    6.     ,max(ol_amount)             max_amount
    7. FROM ordl
    8. GROUP BY ol_w_id  ORDER BY ol_w_id ;
    10. +---------+-------------+------------+------------+------------+------------+
    11. | OL_W_ID | ORDER_COUNT | SUM_AMOUNT | AVG_AMOUNT | MIN_AMOUNT | MAX_AMOUNT |
    12. +---------+-------------+------------+------------+------------+------------+
    13. |       1 |         297 |  917174.33 |    3088.13 |          0 |    9876.11 |
    14. |       2 |         329 | 1153354.23 |    3505.64 |          0 |    9979.34 |
    15. +---------+-------------+------------+------------+------------+------------+
    16. 2 rows in set (0.01 sec)
    18. SELECT ol_w_id, ol_d_id
    19.     ,  count(*)                 order_count
    20.     , sum(ol_amount)            sum_amount
    21.     , round(avg(ol_amount),2)   avg_amount
    22.     , min(ol_amount)            min_amount
    23.     ,max(ol_amount)             max_amount 
    24. FROM ordl  
    25. GROUP BY ol_w_id  
    26. ORDER BY ol_w_id;
    28. ERROR-00979: 'TPCC.ORDL.OL_D_ID' not a GROUP BY expression
    29. obclient>