How to find expected results from SQL queries

I am currently writing a C++ application to parse and execute SQL statements. I have got so far with it but now I am finding it difficult to continue because I don’t known what should happen in certain situations, for example with table joins, like in:

SELECT col1.table1, col2.table2 
FROM table1, table2;

with no explicit JOIN specified.

Is there a website or book or something I can refer to to find what’s supposed to happen in particular circumstances? I have found one or two web sites that allow interactive SQL but they are more concerned with correct syntax etc.

I want to be able to find what should happen, even (especially) if it just means an appropriate error message.

Answer

You didn’t specify what type of SQL server you were working with, but MySQL is free, and some commercial SQL vendors have free developer versions of their products. Install it and try it out.