CREATE FUNCTION UNIX_TIMESTAMP (
@ctimestamp datetime
)
RETURNS integer
AS 
BEGIN
  /* Function body */
  declare @return integer

  SELECT @return = DATEDIFF(SECOND,{d '1970-01-01'},@ctimestamp)

  return @return
END

或这篇文章：

http://mysql.databases.aspfaq.com/how-do-i-convert-a-sql-server-datetime-value-to-a-unix-timestamp.html

代码如下：

CREATE FUNCTION dbo.DTtoUnixTS 
( 
    @dt DATETIME 
) 
RETURNS BIGINT 
AS 
BEGIN 
    DECLARE @diff BIGINT 
    IF @dt >= '20380119' 
    BEGIN 
        SET @diff = CONVERT(BIGINT,DATEDIFF(S,'19700101','20380119')) 
            + CONVERT(BIGINT,'20380119',@dt)) 
    END 
    ELSE 
        SET @diff = DATEDIFF(S,@dt) 
    RETURN @diff 
END

样品用量：

SELECT dbo.DTtoUnixTS(GETDATE()) 
-- or 
SELECT UnixTimestamp = dbo.DTtoUnixTS(someColumn) 
    FROM soMetable