按顺序添加下一个min（Date）的值

Question

我正在用ID的前3次访问高度值更新表格，例如...

ID fvdate访问Ht_date Ht_value

1 06jun2010 1 06jun2010 168
1 06jun2010 2 18Dec2010 168.2
1 06jun2010 3 ?         ?
2 12dec2011 1 25dec2011 175
2 12dec2011 2 12feb2012 175.8
2 12dec2011 3 ?         ?

对于前2次访问，我进行了很好的更新。 但是在更新第3次访问时，我遇到了一些麻烦...

我使用以下代码用日期更新值

update mytab
set ht_DT = b.Record_date,
ht = b.Height
FROM mytaba JOIN anthropometry b
ON a.mno = b.patient_id and Visit ='1' and
b.record_date = fvdate 

update mytabset 
ht_DT = b.Record_date, 
ht = b.Height 
FROM mytaba JOIN anthropometry b 
ON a.mno = b.patient_id and Visit ='2' and 
b.record_date = (select min(record_date) from anthropometry cc where
a.mno = cc.patient_id and cc.record_date > fvdate)

update mytabset ht_DT = b.Record_date, ht = b.Height FROM
mytaba JOIN anthropometry b ON a.mno =
b.patient_id and Visit ='3' and b.record_date =
(select min(record_date) from anthropometry cc where
a.mno = cc.patient_id  and cc.record_date > a.ht_Dt and Visit ='2')

请更正我在给定代码上的错误。