Question

我在密钥date_insert上分区了大约100亿条记录。

MY_BIG_TABLE

id NUMERIC二级索引
date_insert DATE主索引
date_fact DATE二级索引
数据BLOB

输入：

：date_input1
：date_input2
：date_input3
：ID

注意：:date_input1 < :date_input2

我想要

IF date_fact < :date_input_1按date_fact DESC
ELSE IF date_fact < :date_input_2按date_fact ASC
ELSE最新的

查询原型应该是：

SELECT date_insert, date_fact, data (

        SELECT
            date_insert, 
            date_fact,
            CASE 
               WHEN (date_fact < :date_input_1 AND id= :id) : 2
               WHEN (date_fact < :date_input_2 AND id= :id) : 1
               ELSE : 0  
            check,

            CASE 
               WHEN (date_fact < :date_input_1 AND id= :id) : NULL
               WHEN (date_fact < :date_input_2 AND id= :id) : data
               ELSE : NULL  
            data

        FROM MY_BIG_TABLE
        WHERE date_insert > :date_input3   
        order by check, DECODE(check, 1, date_fact) ASC,
                        date_fact DESC 

) WHERE ROWNUM <2

我需要做这项艰苦的工作，以避免过多访问此表。 要完全重建查询的任何建议更简单，更容易吗？

Answer 1

你只想找一排。那么，做三个不同的子查询，每个子查询一行，然后选择你想要的那个：

select date_insert, date_fact, data
from (select date_insert, date_fact, data
      from ((select date_insert, date_fact, data, 2 as check
             from (select date_insert, date_fact,
                          (CASE WHEN (date_fact < :date_input_1 AND id= :id) then NULL
                                WHEN (date_fact < :date_input_2 AND id= :id) then data
                                ELSE NULL
                           end) as data
                   from MY_BIG_TABLE
                   where date_fact < :date_input_1 and date_insert > :date_input3
                   order by date_fact desc
                  ) t
             where rownum = 1
            ) union all
            (select date_insert, date_fact, data, 1 as check
             from (select date_insert, date_fact,
                          (CASE WHEN (date_fact < :date_input_1 AND id= :id) then NULL
                                WHEN (date_fact < :date_input_2 AND id= :id) then data
                                ELSE NULL
                           end) as data
                   from MY_BIG_TABLE
                   where date_fact < :date_input_2 and date_insert > :date_input3
                   order by date_fact asc
                  ) t
             where rownum = 1
            ) union all
            (select date_insert, date_fact, data, 0 as check
             from (select date_insert, date_fact,
                          (CASE WHEN (date_fact < :date_input_1 AND id= :id) then NULL
                                WHEN (date_fact < :date_input_2 AND id= :id) then data
                                ELSE NULL
                           end) as data
                   from MY_BIG_TABLE
                   where date_insert > :date_input3
                   order by date_fact desc
                  ) t
             where rownum = 1
            )
           ) t
      order by check desc
     ) t
where rownum = 1;

Oracle应该足够聪明，可以使用子查询的索引，因此这可能实际上运行得非常快。

分区表上的Oracle SQL高效查询：“逐个案例”

1 个答案: