sql - 如何在oracle 12c中的单个选择中计算每个范围分区的记录？

Question

我正在寻找的解决方案(如果存在)是直接按实际分区和 进行分区。不是 按计算值。

表伪代码:

create table table_1 as (part_col DATE, val_col VARCHAR2(1))
partition by range part_col (
   PARTITION t_20160515 VALUES LESS THAN (TO_DATE('2016-05-15','YYYY-MM-DD'))
   PARTITION t_20160516 VALUES LESS THAN (TO_DATE('2016-05-16','YYYY-MM-DD'))
   ...
);

选择伪代码:

select partition as P, count(*) as C from table_1
group by partition;

想要的结果

  P        |  C
-----------|-----
2016-05-15 | 8
2016-05-16 | 99

有效但不是我想要的:

select trunc(part_col) P, count(*) C from table_1;

Answer 1

运行它为每个分区生成一组选择

SELECT 'SELECT ' || chr(39) || partition_Name || chr(39) || ', count(*) 
        FROM ' ||table_name ||' partition (' || partition_name || 
        ') UNION ALL ' as test 
FROM all_tab_partitions 
WHERE table_Name = 'Table_1'

结果如下:

SELECT 'P1', count(*) FROM Table_1 partition (P1) UNION ALL 
SELECT 'P2', count(*) FROM Table_1 partition (P2) UNION ALL 
SELECT 'P3', count(*) FROM Table_1 partition (P3) UNION ALL 
SELECT 'P4', count(*) FROM Table_1 partition (P4) UNION ALL 
SELECT 'P5', count(*) FROM Table_1 partition (P5) UNION ALL

复制并粘贴结果，删除最后一个联合，然后运行。不太确定性能...我打了一个有 5 个分区的表，它在大约 2 秒内完成，总行数只有大约 500 万。