Shubham is right. However, as no row will be deleted. Also, the code created once will never be assigned to any other space. It wont matter!
Formula : LM-categorycode-citycode-current_index e.g. "LM-CW-DELHI-000000001" # Remove dashses from the string, they are added only to make it easier to understand String after the citycode is called as current_index and it has to be of a standard length e.g. 9. We will call this length as Z_FILL_INDEX. You can modify this Z_FILL_INDEX as required. Hence, Z_FILL_INDEX = 9. In above example, current_index = "000000001" As no row will be deleted, also, the code created once will never be assigned to any other space Hence, current_index will be 1 or plus 1 of the latest one Below code is for django ORM, IDK sqlalchemy version of it :P I dont see how Space is related to a City, you can figure that part yourself. if current_index > 999999999, code will break. 10 Cr is a big no. However, if current_index could be bigger than that, pick a bigger no for Z_FILL_INDEX. In case you run out of index in the future, you can write a script to add few extra zeros to current index part of the code or add pick a bigger no for Z_FILL_INDEX initially e.g. 12. MUST DO : ADD UNIQUE CONSTRAINT ON THE name FIELD OF THE Spaces Model. Z_FILL_INDEX = 9 last_code = Spaces.objects.filter(space_category="blah").order_by( "-created_at").first() if last_code is None: current_index = "1".zfill(Z_FILL_INDEX) else: current_index = str(int(last_code[-Z_FILL_INDEX:]) + 1) unique_code ="LM" + categorycode + citycode + current_index Regards, Chetan Ganji +91-900-483-4183 ganji.che...@gmail.com http://ryucoder.in On Fri, Feb 19, 2021 at 6:16 PM shubham vashisht <shubhva...@gmail.com> wrote: > If there are 4 rows which have categorycode="blah" and > citycode="blah-blah", then the space code will be something like this, > LMblahblah-blah1, LMblahblah-blah2, LMblahblah-blah3, LMblahblah-blah4. > But if you delete row with spacecode different from LMblahblah-blah4, then > your code will generate space code LMblahblah-blah4 > > On Fri, 19 Feb 2021, 16:07 Chetan Ganji, <ganji.che...@gmail.com> wrote: > >> Yes kritika show all the models. >> >> How shubham? >> If an entry is deleted, unique code will also be deleted. Next time it >> gets generated, it might be assigned to different entry, but it still be >> unique. >> >> As kritika clarified already, so it wont be a problem. >> >> On Fri, Feb 19, 2021, 3:58 PM shubham vashisht <shubhva...@gmail.com> >> wrote: >> >>> Chetan >>> If any row is deleted from the table, then your logic will fail to >>> return the unique code >>> >>> On Fri, 19 Feb 2021, 15:52 Chetan Ganji, <ganji.che...@gmail.com> wrote: >>> >>>> Hi Kritika >>>> >>>> Ye chanel mein firangi log bhi hai, unko hinglish kaisa samjhenga? 😂 >>>> >>>> Teko field pe unique constraint lagana padenga >>>> >>>> Teko no wapas 1 se start karneke liye query maarana padenga >>>> >>>> last_no = Model.objects.filter(categorycode="blah", >>>> citycode="blah-blah").count() >>>> >>>> unique_code ="LM" + categorycode >>>> + citycode + str(last_no + 1) >>>> >>>> >>>> Aisa code likkha toh result milenga 😋 >>>> >>>> >>>> On Fri, Feb 19, 2021, 3:31 PM Kritika Paul <rkritikapau...@gmail.com> >>>> wrote: >>>> >>>>> I have to create a unique code for each space saved in dbAb db me >>>>> save krne k lie, wo multiple part me save ho rha hai, multiple models bhi >>>>> hai uske.1st model se mujhe space category ka name uthana hai >>>>> 2nd se city code >>>>> Category alag alg ho skti hai >>>>> To code genrate hoga LM-categorycode-citycode-00001Next time jb >>>>> category, B hogi to number 1 se hi start hoga, ni to category same hai to >>>>> fr se 2 allot ho jaega >>>>> Eg Category - CW, COM >>>>> City - Noida, DelhiSpace 1 - Cw category >>>>> Code space 1- LMCWNoida00001Space2 - CW Category >>>>> CODE SPACE2 - LMCWDelhi00002Space 3 - COM category >>>>> CODE SPACE 3- LM-COM-NOIDA0001 >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Django users" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to django-users+unsubscr...@googlegroups.com. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/django-users/690debd2-46e0-497f-92a8-3abbc391b97dn%40googlegroups.com >>>>> <https://groups.google.com/d/msgid/django-users/690debd2-46e0-497f-92a8-3abbc391b97dn%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Django users" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to django-users+unsubscr...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/django-users/CAMKMUjs6q%2B6Xer6-MRu%3DYjhKq5EYNXahEji%2BY5HBerTaNQ1Law%40mail.gmail.com >>>> <https://groups.google.com/d/msgid/django-users/CAMKMUjs6q%2B6Xer6-MRu%3DYjhKq5EYNXahEji%2BY5HBerTaNQ1Law%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Django users" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to django-users+unsubscr...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/django-users/CAJW_r64v1-f85ViX%2BnCFdBrupiXi5Ba%3Dzec6xoSvuZnR1jaMEg%40mail.gmail.com >>> <https://groups.google.com/d/msgid/django-users/CAJW_r64v1-f85ViX%2BnCFdBrupiXi5Ba%3Dzec6xoSvuZnR1jaMEg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "Django users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to django-users+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-users/CAMKMUjsJR2B7LDHujo_bXxyh1s7WZMqMwgENMQmwiX%3Dpe5QHTg%40mail.gmail.com >> <https://groups.google.com/d/msgid/django-users/CAMKMUjsJR2B7LDHujo_bXxyh1s7WZMqMwgENMQmwiX%3Dpe5QHTg%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to django-users+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/CAJW_r671m7KANhpAdSPuG7AabVacUOsVcgdhPgH2j8HruNkOgQ%40mail.gmail.com > <https://groups.google.com/d/msgid/django-users/CAJW_r671m7KANhpAdSPuG7AabVacUOsVcgdhPgH2j8HruNkOgQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Django users" group. 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