datetime 可以精确到毫秒,而smalldatetime 只精确到分钟。select cast(getdate() as datetime)select cast(getdate() as smalldatetime)                                                       
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2003-05-23 22:57:31.397(所影响的行数为 1 行)                                                       
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2003-05-23 22:58:00(所影响的行数为 1 行)