Question on database structure

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Hi people,

I want to migrate some old mysql-databases to postgresql.
With this step I want to optimize some database structures.

I have a (mysql-) database with all zip-codes and cities in germany.
As there are a lot of them I decided to split them in more tables at that time.
So now there are 10 tables with zip-codes (those starting with '0' in one table, those starting with '1' in another table, and so on).

I also have all streets of germany with their corresponding zip code.
Like the zip-code tables the streets are also splitted in 10 tables (same scheme as above).

My question now is, whether to keep that structure or to throw them together in two big tables?
For accessing that data it would be easier to make two tables, but I don't know what about performance (cause the street-table would have something about one million tuples)?

Thank you for your help!

Greetings,
Simon
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