关于Group问题

Question

<P>PKId Title Datatime B_PIKd</P> <P>1&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp; &nbsp;2<BR>2&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp;&nbsp; 1<BR>3&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp;&nbsp; &nbsp;2<BR>4&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp;&nbsp; 3<BR>5&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp; &nbsp;3<BR>6&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp;&nbsp; 3<BR>7&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp;&nbsp; 3<BR>8&nbsp;title&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;NULL&nbsp; &nbsp;1</P> <P>&nbsp;</P> <P>select * from News group by B_PKId&nbsp; 这条为什么报错</P> <P>消息 8120，级别 16，状态 1，第 1 行<BR>选择列表中的列 'News.PKId' 无效，因为该列没有包含在聚合函数或 GROUP BY 子句中。</P>

Answer 1

GROUP BY 是配合聚合语句用的 select count（*） , B_PKId from News group by B_PKId 只group by中能够不用聚合函数表示的只有被group by 的项