Question

以下代码返回员工出生的年份：

CREATE OR REPLACE FUNCTION Convert_Year_to_Year (Convert_Date IN Date)
       RETURN Varchar2 AS
BEGIN
       RETURN (To_Char (Convert_Date, ‘YEAR’));
END;
/

当我使用SELECT命令检索数据时，将显示以下输出：

Select employee_id, hiredate,  Convert_year_to_year (hiredate) AS Year_Hired 
FROM employees;

EMPLOYEE_ID HIREDATE    YEAR_HIRED
       1    12/17/2007  TWO THOUSAND SEVEN
       2    02/20/2008  TWO THOUSAND EIGHT
       3    02/22/2008  TWO THOUSAND EIGHT
       4    04/02/2008  TWO THOUSAND EIGHT
       5    09/28/2008  TWO THOUSAND EIGHT
       6    05/01/2008  TWO THOUSAND EIGHT
       7    06/09/2008  TWO THOUSAND EIGHT
       8    12/09/2008  TWO THOUSAND EIGHT
       9    09/08/2007  TWO THOUSAND SEVEN
      10    01/12/2007  TWO THOUSAND SEVEN

如何将“YEAR_HIRED”更改为2007年的数字年份？
如何更改“YEAR_HIRED”以返回当天的名称以及星期几？

另外，如果我想组合所有RETURN，我该如何编写代码？下面没有用

CREATE OR REPLACE FUNCTION Convert_Year_to_Year (Convert_Date IN Date)
     RETURN Varchar2 AS
BEGIN
     RETURN (To_Char (Convert_Date, 'YYYY'),
     RETURN (To_Char (Convert_Date, 'DAY'),
     RETURN (To_Char (Convert_Date, 'D'));
END;
/

EMPLOYEE_ID HIREDATE    YEAR_HIRED DAY_HIRED  NUMERICAL_DAY_OF_WEEK
       1    12/17/2007  2007       MONDAY      1
       2    02/20/2008  2008       WEDNESDAY   3
       3    02/22/2008  2008       FRIDAY      5
       4    04/02/2008  2008       WEDNESDAY   5
       5    09/28/2008  2008       SUNDAY      7

Answer 1

获取数字年份（例如2007）：

TO_CHAR(Convert_Date, 'YYYY')

获取星期几的名称（例如SATURDAY）：

TO_CHAR(Convert_Date, 'DAY')

获取星期几的数值（例如7）：

TO_CHAR(Convert_Date, 'D')

如果你真的以非标准的方式得到一周的数值（例如星期一= 1，星期六= 6，星期日= 7），那么这种丑陋就会起作用：

to_char(decode(to_number(to_char(Convert_Date, 'D')) - 1, 0, 7, to_number(to_char(Convert_Date, 'D')) - 1))

修改

要将3位信息作为查询的3个单独列返回，您需要创建3个单独的函数，或者，只需编写此查询而不使用函数，这对您来说无论如何都不会做很多事情（但是你你的函数中不能有3个return语句：

Select employee_id, hiredate, TO_CHAR(hiredate, 'YYYY') AS Year_Hired, TO_CHAR(hiredate, 'DAY') AS DAY_HIRED, decode(to_number(to_char(hiredate, 'D')) - 1, 0, 7, to_number(to_char(hiredate, 'D')) - 1) AS NUMERICAL_DAY_OF_WEEK FROM employees;

如何将CRE_ OR REPLACE函数更改为Convert_Year_to_Year到Day_to_Day

1 个答案: