每一次会面以一个称为 event的状态码结束。下面显示的查询被用来显示按事件组合的所有孪生的表。这表明多少对孪生已经完成，多少对的其中之一已完成而另一个拒绝了，等等。

SELECT

        t1.event,

        t2.event,

        COUNT(*)

FROM

        lentus AS t1,

        lentus AS t2,

        twin_project AS tp

WHERE

        /* We are looking at one pair at a time */

        t1.id = tp.id

        AND t1.tvab=tp.tvab

        AND t1.id = t2.id

        /* Just the screening survey */

        AND tp.survey_no = 5

        /* This makes each pair only appear once */

        AND t1.tvab='1' AND t2.tvab='2'

GROUP BY

        t1.event, t2.event;