如何使用带有 select 语句的 UDF？

Question

我创建了一个标量用户定义函数，它将接受出生日期和 return 一个人从现在起 15 年后的年龄。

CREATE FUNCTION AgeIn15 (@DateOfBirth DATE)
RETURNS INT
AS
BEGIN
    RETURN Convert(INT, DateAdd(year, 15, DateDiff(year, @DateOfBirth, GetDate())))
END

现在我想使用创建的 UDF 来显示我 table marketing_list 中所有人的年龄及其原始信息。我该怎么做呢？我试过了，但出现错误

SELECT *
FROM marketing_list AgeIn15(marketing_list.DateOfBirth)

SELECT *
    ,AgeIn15(marketing_list.Date_of_Birth)
FROM marketing_list
WHERE AgeIn15(Date_of_Birth) > 45

Answer 1

添加架构名称：

SELECT *, dbo.AgeIn15(m.Date_of_Birth) AS col_name
FROM marketing_list AS m;

SELECT *
    ,dbo.AgeIn15(m.Date_of_Birth) AS col_name
FROM marketing_list m
WHERE dbo.AgeIn15(m.Date_of_Birth) > 45

您可以选择使用 CROSS APPLY:

Select *
from marketing_list AS m
CROSS APPLY (SELECT dbo.AgeIn15(m.Date_of_Birth)) AS c(col_name)

Demo

SELECT  *, dbo.AgeIn15(t.c) AS col_name
FROM (SELECT '2000-01-01') AS t(c);

SELECT  *
FROM (SELECT '2000-01-01') AS t(c)
CROSS APPLY (SELECT dbo.AgeIn15(t.c)) AS c(col_name)

您的函数应该如下所示：

CREATE FUNCTION dbo.AgeIn15 (@DateOfBirth DATE)
RETURNS INTEGER
AS
BEGIN
    RETURN DATEDIFF(year,@DateOfBirth,GETDATE()) + 15
END

你所做的没有任何意义：

Convert(integer,DateAdd(year,15,DateDiff(year,@DateOfBirth,GetDate())))

计算 DATEDIFF - 它 returns 数年 OK
DATEADD(year, 15, number) - returns 日期 15 年 + 1900-01-number FAIL
CONVERT(INTEGER, DATE) - 从 1900-01-01 开始的 returns 天数 FAIL

Answer 2

CREATE FUNCTION AgeIn15 (@DateOfBirth DATE)
RETURNS INT
AS
BEGIN
    RETURN 
       -- get the year today + 15 years
       (
          (DATEPART(YEAR, GETDATE() ) + 15) - 
          -- minus the year of date of birth
          DATEPART(YEAR,@DateOfBirth)
       )
       -- its like saying (2015 + 15)-09-29 - (1990)-09-19 = 40
END

SELECT *
    , dbo.AgeIn15(mlist.Date_of_Birth) AS [AgeAfterFifteenYears]
FROM marketing_list AS mlist

希望这对您有所帮助

如何使用带有 select 语句的 UDF？

How do I use a UDF with a select statement?

sql-server

user-defined-functions