假设你有下表(这里感兴趣的列是cid):+-----+-------+-------+-------+---------------------+--------------+|cid|pid|rid|clink|time|snippet|+-----+-------+-------+-------+---------------------+--------------+|155|11222|1499|1137|2012-08-2203:05:06|hi||138|11222|241|1136|2012-08-2105:25:00|again||138|11222|241|1135|
