Change teaching join

[Rick]

Hi

I have changed the teaching of the join command to use the JOIN keyword explicitly 

old format

SELECT * FROM stock, nation

WHERE stock.natcode = nation.natcode;

new format

SELECT * FROM stock JOIN nation

ON stock.natcode = nation.natcode;

This should help to avoid the situation where students forget to specify the join condition. 

A new version of the book should appear within 12 hours.

I have revised the slides and answers to exercises. If you find something I have missed, please let me know.

Cheers  

Rick