關於SQL表字段值缺失的處理辦法

在計算收益率時候，  收益率 = 收益 / 成本

一、如果成本為0，NULL，此時無法計算收益率；

方法：

1.將成本為0的數據 運算

(case when  cost =0 or cost is null then 0  else  income/cost end) as yeild;

select account,sum(case when amount1 is null then 0 else amount1 END) as total,init_date 
from data_stock1 GROUP BY account,init_date;

SELECT
    account,
    CASE
WHEN min(amount1) <= 0 THEN
    '零'
WHEN min(amount1) <= 100 THEN
    '十'
WHEN min(amount1) <= 1000 THEN
    '百'
ELSE
    '百以上'
END AS 級別,
 init_date
FROM
    data_stock1
GROUP BY
    account,
    init_date;

 

2.處理數據為NULL時的運算：

將數據轉化為 0； nvl(cost, 0) as cost;

3.四舍五入 

round(cost,4)

4.取整

ceil(cost) 

floor(cost) 

二、計算數據

 

三、探討UNION ALL與FULL JOIN ON 運用同一場景的效率問題

[轉]http://www.zhixing123.cn/net/27495.html

　　一、查詢執行最慢的sql

select *
 from (select sa.SQL_TEXT,
        sa.SQL_FULLTEXT,
        sa.EXECUTIONS "執行次數",
        round(sa.ELAPSED_TIME / 1000000, 2) "總執行時間",
        round(sa.ELAPSED_TIME / 1000000 / sa.EXECUTIONS, 2) "平均執行時間",
        sa.COMMAND_TYPE,
        sa.PARSING_USER_ID "用戶ID",
        u.username "用戶名",
        sa.HASH_VALUE
     from v$sqlarea sa
     left join all_users u
      on sa.PARSING_USER_ID = u.user_id
     where sa.EXECUTIONS > 0
     order by (sa.ELAPSED_TIME / sa.EXECUTIONS) desc)
 where rownum <= 50;

　　二、查詢次數最多的 sql

select *
 from (select s.SQL_TEXT,
        s.EXECUTIONS "執行次數",
        s.PARSING_USER_ID "用戶名",
        rank() over(order by EXECUTIONS desc) EXEC_RANK
     from v$sql s
     left join all_users u
      on u.USER_ID = s.PARSING_USER_ID) t
 where exec_rank <= 100;

 四、關於兩表出現 null值的字段加減