Compabatible SQL Server for POS4

may i know which is best server compatible with SambaPOS 4? 32/64 bit

SQL 2012 Business Intelligent
SQL 2012Enterprise
SQL 2012Express

SQL 2012Express studio

All of them are compatible. You can start with free express version and upgrade later when needed.

PS: Free express version have database size limits. In my home city a 24hr. open busy restaurant uses express version for more than 3 years and they couldn’t even reached near express version limits.

There is no need to buy the full version of SQL Server.
SQL Express works perfectly with SambaPOS. Especially the 2012 version.
The following document (even though it was written for V3) steps you through the setup.