problem with a query

hi to all

i need to do a query to a small postgres database
my best efort to the pretended query is in the attached file 'query.txt'
but i need that some rows don't be selected of thouse that the query
returns.

i send in another attached file 'result.txt' with the query result. looking
at content of the file you will see some notes at the end of the table (#..)

the database as the data to enable the constrution of a school class
schedule.

In the 'result.txt' all the rows with max=0 were the fisrt to be inserted do
the database. each row represent as example math pratical starting at 8:30
for 1:30 at room 3.15 in the bilding CP

the rows with max!=0 (1,2,3,...) mean that content of an insert with max=0
was changed [ex diferent time (fiel to_char) or room (field sala) or bilding
(field edificio)of the school class]. row with max=1 is a substitution to a
row with max=0, row with max=2 substitutes row with max=1 and ...

my objective is to obtain all the rows that were not substituted and the
ones that represent the last alteration to the shedule

i hope the problem was understod
thanks for your time

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