我目前有一个表格函数，用于删除重复的雇主条目并更新结束日期。
目前我的表如下
Memberid startdate enddate Employerid
10220 1978-08-07 2007-12-31 1153
10220 2008-01-01 2011-06-16 1811
10220 2011-06-17 2011-06-30 1124
10220 2011-07-01 2011-07-18 1124
10220 2011-07-19 2011-07-31 1178
10220 2011-08-01 2011-08-17 1178
10220 2011-08-18 2011-09-18 1124
10220 2011-09-19 2011-10-18 1124
10220 2011-10-19 2011-11-16 1124
10220 2011-11-17 2011-12-12 1124
10220 2011-12-13 2012-01-18 1124
10220 2012-01-19 2012-02-16 1124
10220 2012-02-17 2012-03-18 1124
10220 2012-03-19 2012-04-18 1124
10220 2012-04-19 NULL 1124
我想通过一个表值函数放入一个计数器，以便每次更换雇主时计数
例如
Memberid startdate enddate Employerid Count
10220 1978-08-07 2007-12-31 1153 1
10220 2008-01-01 2011-06-16 1811 2
10220 2011-06-17 2011-06-30 1124 3
10220 2011-07-01 2011-07-18 1124 3
10220 2011-07-19 2011-07-31 1178 4
10220 2011-08-01 2011-08-17 1178 4
10220 2011-08-18 2011-09-18 1124 5
10220 2011-09-19 2011-10-18 1124 5
10220 2011-10-19 2011-11-16 1124 5
10220 2011-11-17 2011-12-12 1124 5
10220 2011-12-13 2012-01-18 1124 5
10220 2012-01-19 2012-02-16 1124 5
10220 2012-02-17 2012-03-18 1124 5
10220 2012-03-19 2012-04-18 1124 5
10220 2012-04-19 NULL 1124 5