advanced concatenation of lines based on the specific number of compared columns in csv - bash

Question

this is the question based on the previous solved problem.
i have the following type of .csv files(they aren't all sorted!, but the structure of columns is the same):
name1,address1,town1,zip1,email1,web1,,,,category1
name2,address2,town2,zip2,email2,,,,,category2
name3,address3,town3,zip3,email3,,,,,category3_1
name3,address3,town3,zip3,,,,,,category3_2
name3,address3,town3,zip3,,,,,,category3_3
name4,address4,town4,zip4,,,,,,category4_1
name4,address4,town4,zip4,email4,,,,,category4_2
name4,address4,town4,zip4,email4,,,,,category4_3
name4,address4,town4,zip4,,,,,,category4_4
name5,address5,town5,zip5,,,,,,category5_1
name5,address5,town5,zip5,,web5,,,,category5_2
name6,address6,town6,zip6,,,,,,category6
first 4 records in columns are always populated, other columns are not always, except the last one - category
empty space between "," delimiter means that there is no data for the particular line or name
if the nameX doesnt contain addressX but addressY, it is a different record(not the same line) and should not be concatenated
i need the script in sed or awk, maybe the bash(but this solution is little slower on bigger files[hundreds of MB+]), that will take first 4 columns(in this case) compares them and if matched, will merge every category with the ";" delimiter and will keep the structure and the most possible data in other columns of those matched lines of a .csv file:
name1,address1,town1,zip1,email1,web1,,,,category1
name2,address2,town2,zip2,email2,,,,,category2
name3,address3,town3,zip3,email3,,,,,category3_1;category3_2;category3_3
name4,address4,town4,zip4,email4,,,,,category4_1;category4_2;category4_3;category4_4
name5,address5,town5,zip5,,web5,,,,category5_1;category5_2
name6,address6,town6,zip6,,,,,,category6
if that is not possible, solution could be to retain data from the first line of the duped data(the one with categoryX_1). example:
name1,address1,town1,zip1,email1,web1,,,,category1
name2,address2,town2,zip2,email2,,,,,category2
name3,address3,town3,zip3,email3,,,,,category3_1;category3_2;category3_3
name4,address4,town4,zip4,,,,,,category4_1;category4_2;category4_3;category4_4
name5,address5,town5,zip5,,,,,,category5_1;category5_2
name6,address6,town6,zip6,,,,,,category6
does the .csv have to be sorted before using the script?
thank you again!

Answer 1

sed -n 's/.*/²&³/;H
$ { g
:cat
s/\(²\([^,]*,\)\{4\}\)\(\([^,]*,\)\{5\}\)\([^³]*\)³\(.*\)\n\1\(\([^,]*,\)\{5\}\)\([^³]*\)³/\1~\3~ ~\7~\5;\9³\6/
t fields
b clean
:fields
s/~\([^,]*\),\([^~]*~\) ~\1,\([^~]*~\)/\1,~\2 ~\3/
t fields
s/~\([^,]*\),\([^~]*~\) ~\([^,]*,\)\([^~]*~\)/\1\3~\2 ~\4/
t fields
s/~~ ~~//g
b cat
:clean
s/.//;s/[²³]//g
p
}' YourFile
Posix version (so --posixwith GNU sed) and without sorting your file previously
2 recursive loop after loading the full file in buffer, adding marker for easier manipulation and lot of fun with sed group substitution (hopefully just reach the maximum group available).
loop to add category (1 line after the other, needed for next loop on each field) per line and a big sub field temporary structured (2 group of field from the 2 concatened lines. field 5 to 9 are 1 group)
ungroup sub field to original place
finaly, remove marker and first new line
Assuming there is no ²³~ character because used as marker (you can use other marker and adapt the script with your new marker)
Note:
For performance on a hundred MB file, i guess awk will be lot more efficient.
Sorting the data previoulsy may help certainly in performance reducing amount of data to manipulate after each category loop

Answer 2

i found, that this particular problem is faster being processed through db...
SQL - GROUP BY to combine/concat a column
db: mysql through wamp