SQL query to fetch data from last visit of particular column -


i have table columns regno,dt,visitno , symptom_code. i'd fetch data last visit of regno. please suggest sql query.

every dbms supports this:

select * tab t1 dt =  ( select max(dt) tab t2    t1.regno = t2.regno)

most dbmses support windowed aggregate functions, easier write , more efficient:

select *   ( select ...      ,rank()        on (partition regno             order dt desc) rnk     tab  ) dt rnk = 1

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