Question

我想显示今年每月的总访问量。但是以下查询返回缺少表达式的错误代码。我错过了什么？

 SELECT CASE 
     WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '),     'mm/dd/yyyy')  = 1 THEN 'January '
     WHEN extract(month from date  TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '),   'mm/dd/yyyy')  = 2 THEN 'February'
WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 3 THEN 'March'
WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 4 THEN 'April'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 5 THEN 'May'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 6 THEN 'June'
WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 7 THEN 'July'
WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 8 THEN 'August'
WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 9 THEN 'September'
WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 10 THEN 'October'   
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 11 THEN 'November'   
 ELSE 'December'
    END AS "Month " , 
    COUNT(*) AS "Number of visits"
 FROM allrecord where  extract(year from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')= extract(year from date sysdate) 
 GROUP BY CASE 
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 1 THEN 'January '
     WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 2 THEN 'February'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 3 THEN 'March'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 4 THEN 'April'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 5 THEN 'May'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 6 THEN 'June'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 7 THEN 'July'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 8 THEN 'August'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 9 THEN 'September'
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 10 THEN 'October'   
 WHEN extract(month from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')  = 11 THEN 'November'   

       ELSE 'December'
          END;

要问的另一个问题是，我正在使用ORacle应用程序构建器创建应用程序。但是在我创建页面并想要编辑表单中的记录之后，会显示一条错误消息，表明可以获取数据。这是什么意思？我错过了任何步骤？

Answer 1

此查询都可以缩减为：

  select to_char(VISIT_TIME, 'fmMonth') as "Month"
        ,count(*) as "Number of Visits"
    from ALLRECORD
   where extract(year from VISIT_TIME) = extract(year from sysdate)
group by to_char(VISIT_TIME, 'fmMonth');

缺少表达式错误的原因是将关键字date放在to_date函数的extract前面。这是不必要的。你可以使用：

select extract (year from date '2011-01-01') from sys.dual

或：

select extract (year from to_date('2011-01-01')) from sys.dual

但永远不会：

select extract (year from date to_date('2011-01-01')) from sys.dual

Answer 2

Oracle是否具有从以下日期中提取月份名称的功能：

SELECT TO_CHAR(visit_time 'MONTH') as month
COUNT(*) AS "Number of visits"
FROM allrecord 
WHERE  extract(year from date TO_DATE (TO_CHAR (visit_time, 'mm/dd/yyyy '), 'mm/dd/yyyy')= extract(year from date sysdate) 
GROUP BY TO_CHAR(visit_time 'MONTH')

显示今年每月的访问次数

2 个答案: