在数据库中根据身份证号算出生日期

update Staff_information set

csny = 

case when LEN(sfzh)=18 then  (substring(sfzh,7,4) +'-'+  substring(sfzh,11,2)+'-'+ substring(sfzh,13,2)) 

 when LEN(sfzh)=15 then ('19' + substring(sfzh,7,2) +'-'+  substring(sfzh,9,2)+'-'+ substring(sfzh,11,2))

 else null

end

 from Staff_information