Choosing database for a POS

While developing an open source product its important to consider a matching database engine. Fortunately there are a number of stable database system already tested and recognized both web and Java applications. For Restaurants we required

1. A Public domain license so that we can distribute DB unconditionally with software.
   
2. Concurrent access - multiple clients may access 
3. Embedded mode preferred ( to run in single work station)
   
4. Database joining, subquery and view especially for reports
   
5. Fast DB transaction but transactions my not be huge
6. Friendly with Java (since we already selected java)
   

Following matix shows a comparison among different DB engines. We have eventually selected Apache Derby because it fulfills most of the features. In addition it can be embedded as well as its license is more flexible than MySQL.

	Apache Derby 10	MySQL 5	PostgreSQL 8	SQLite
Database Connections	Multiple	Multiple	Multiple	Multiple
Concurrent Access to Multiple Databases	√	√	√	√
Embedded Database	√	x	x	√
Unicode Support	√	√	√	√
Replication Support	√	√	√	√
License	Apache (BSD)	GPL	BSD	Public Domain
Specifications
SQL 99	√	x	√	x
SQL 92	√	√	√	x
Relational Database Features
Sequences/A uto-increment Column	√	√	√	x
User Defined Functions	√	√	√	x
Update-capable Views	√	√	√	x
Referential Integrity	√	√	√	x
Triggers Statement / Row Level Before / After Nesting Compound	√	√	√	x
	√	√	√	X
	√	x	√	x
	√	√	√	x
SUBQUERY	√	√	√	x
OUTER JOIN	√	√	√	x
Name Length Limit	128	64	64	255
Delimited Identifiers	√	√	√	√
Stored Procedures	√	√	√	√

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