Understanding SQL Server string data types: char vs varchar vs nchar vs nvarchar

Data and Databases
1

I’m working with SQL Server databases and I keep running into different string data types. I understand there are four main ones but I’m confused about when to use each one.

Can someone explain what nvarchar actually means and how it works? Also, what are the key differences between:

  • char
  • nchar
  • varchar
  • nvarchar

I’m trying to design some tables and want to pick the right data type for my text columns. I’ve seen people use different ones but I don’t really understand the pros and cons of each approach. Any help would be great!

CREATE TABLE employees (
    emp_id INT,
    first_name ???, -- which one should I use here?
    last_name ???,  -- and here?
    description ??? -- what about for longer text?
);
2

hmm interesting question! i’m curious about your specific use case though - are you dealing with international data or just english text? that usually helps me decide between the n-types and regular ones. also what’s the expected length of your description field? seems like that might need different handling than names

3

The fundamental distinction comes down to character encoding and storage allocation. nvarchar uses Unicode (UTF-16) encoding, meaning each character consumes 2 bytes regardless of language, while varchar uses single-byte encoding limited to your database collation’s character set. Fixed-length types (char, nchar) pad with spaces to reach their declared size, making them efficient for consistently-sized data but wasteful otherwise. Variable-length types (varchar, nvarchar) only store what you actually input plus overhead bytes. For your employee table, I would recommend nvarchar(100) for both name fields and nvarchar(1000) for description. This approach future-proofs against international characters without significant performance impact on modern systems. The storage overhead of Unicode is typically negligible compared to the flexibility gained, especially when dealing with user-generated content or data that might eventually include non-English text.

4

just a quick note - char/varchar handle only ascii, while nchar/nvarchar are good for unicode (like other languages). they’re fixed length vs variable too. for your table, i’d suggest nvarchar(50) for names and nvarchar(500) for the description unless you’re sure no international stuff will come in!