SQL question - Why use int as a primary key and not varchar?

Question

I have a DB with varchar primary key. It's actual names like "Version 21" Version 532". I didn't create this database and I suggested we change it to have an int primary key and they asked me why?

Answer 1

You can use varchar as a PK, but integers are better for performance. They take up less space, and more importantly they are much quicker to compare.



An integer comparison can be executed in one CPU instruction. For strings, each character must be compared in turn. That makes every PK lookup faster. If you have join tables, every join select will be looking up against the PK.



Still, why did you suggest it without knowing why? It quite reasonable for someone else to ask why when you suggest a change. If you don't know why, you should not suggest it.



If performance is not an issue and you don't expect much DB growth, then I would keep the PK as is.

Answer 2

first of all, the PRIMARY KEY can be ANY DATA TYPE.



but we choose int because it's maximum size is 4, unlike varchar. the primary key is made to decrease redundancy as u know, however i'll insert it in many tables. so i need a small data type to be a primary because i'll repeat it in many tables as foreign key.



another thing is the indexing of int is always faster than the varchar.



and don't forget the calculation that done by the server, SQL server will face difficulties with varchar.



so..

integer is BETTER.



but sometimes u might need a varchar 2 be primary , when u don't need to insert an int out of no where. u don't need an int column, so use the varchar

Answer 3

Primary Key Varchar

Answer 4

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Answer 5

Well if the field has characters in it like the word Version, you'll have to strip that before converting it to int as int can only have numbers.





But I agrea int is much better, espcially if that key is user populated. text feilds are much more likely to fat fingered, mis-spelled or use the wrong case. With numbers, yes people can transpose them but there is less room for error so you're more likely to have consitancey.



Also if you drop the text characters the fields size will be smaller so indexing will take up less system resources.

Answer 6

Varchar can be used as datatype for primarykey. primary key should have unique values inspite of its datatype. only condition is that it should maintain data integrity(uniqueness).

Answer 7

may be they don't like the change or if u really want to do it then don't listen to them.