Question

我是SQL Server的新手。请帮我在查询中编写以下逻辑。

If getnow() > today 4 PM
Then
    SELECT *
    FROM table
    WHERE MailDate is Tomorrow
Else
    SELECT *
    FROM table
    WHERE MailDate is Today

Answer 1

select *
from table
where DATEDIFF(day, GETDATE(), maildate) = case when
    DATEPART(hour, GETDATE()) >= 16 then 1 else 0
end

Answer 2

IF datepart(hh, getdate()) >= 16
    BEGIN
        SELECT *
        FROM table
        WHERE DateDiff(day, getdate(), MailDate) = 1
    END
ELSE
    BEGIN
        SELECT *
        FROM table
        WHERE DateDiff(day, getdate(), MailDate) = 0
    END

Answer 3

我不知道确切的MS语法方言，但我会尝试证明你不需要IF或CASE结构。我以@mellamokb的回复为例。

SELECT *
  FROM the_table
 WHERE ( DATEPART(hour, GETDATE()) >= 16
           AND DATEDIFF(day, GETDATE(), MailDate) = 1)
    OR (DATEPART(hour, GETDATE()) < 16
           AND DATEDIFF(day, GETDATE(), MailDate) = 0)
     ;

Answer 4

这里的想法是使用暗示重写规则：

IF ( x ) THEN ( y )   is equivalent to  ( NOT ( x ) OR y )

在你的情况下

IF ( DATEPART(HOUR, CURRENT_TIMESTAMP) >= 16 ) 
   THEN ( DATEDIFF(DAY, CURRENT_TIMESTAMP, MailDate) = 1 )

相当于

( NOT ( DATEPART(HOUR, CURRENT_TIMESTAMP) >= 16 ) 
   OR ( DATEDIFF(DAY, CURRENT_TIMESTAMP, MailDate) = 1 ) )

并且本身等同于

( ( DATEPART(HOUR, CURRENT_TIMESTAMP) < 16 ) 
   OR ( DATEDIFF(DAY, CURRENT_TIMESTAMP, MailDate) = 1 ) )

将原始ELSE子句重写为IF..THEN语句本身：

IF ( DATEPART(HOUR, CURRENT_TIMESTAMP) < 16 ) 
   THEN ( DATEDIFF(DAY, CURRENT_TIMESTAMP, MailDate) = 0 )

等同于（这次省略中间步骤）

( ( DATEPART(HOUR, CURRENT_TIMESTAMP) >= 16 )
   OR ( DATEDIFF(DAY, CURRENT_TIMESTAMP, MailDate) = 0 ) )

然后这两个表达式可以以联合正常形式（“一系列AND s）

进行写作

SELECT *
  FROM the_table
 WHERE ( ( DATEPART(HOUR, CURRENT_TIMESTAMP) < 16 ) 
          OR ( DATEDIFF(DAY, CURRENT_TIMESTAMP, MailDate) = 1 ) ) 
       AND 
       ( ( (DATEPART(HOUR, CURRENT_TIMESTAMP) >= 16
          OR ( DATEDIFF(DAY, CURRENT_TIMESTAMP, MailDate) = 0 ) )  ;

Answer 5

从mytable a中选择a.name，if（a.is_active ='t'，'Active'，'Inactive'）

Answer 6

您需要一个存储过程才能在SQL中执行此操作。请查看此处的文档http://msdn.microsoft.com/en-us/library/aa174792(v=sql.80).aspx

Answer 7

IF ( DATEDIFF(h, GETDATE(), DATEADD(h,4,GETDATE()))>0 )

SELECT *
FROM table
WHERE MailDate is Tomorrow

ELSE

SELECT *
FROM table
WHERE MailDate is Today

这是MS SQL。如果你想做更多，那么只需要一个命令/选择如果你做BEGIN .... END。

Answer 8

IF DATEPART(HOUR, GETDATE()) > 16
BEGIN
    -- SELECT statement
END
ELSE 
BEGIN
    -- SELECT statement
END

它不必存储在存储过程中。

SQL查询中的IF条件

8 个答案: