Hi veryone!
I have a difficluty about query, you can help me solve it. I need the help from you. my question is :

there are two tables with the following data:

M-Manufacturer(MID,MNAME,CITY)

MID MNAME CITY
M1 TOM sydney
M2 Mary Brisbane

P-PRODUCT(PID,PNAME,CITY)

PID PNAME CITY
P1 computer sydney
P2 CD-ROM Perth

Question :get all cities(CITY) in which at least one manufacturer or product.

I understand that according to the question and based on the data above, the result will include the following city : sydney, brishane, perth. this is union operator but I do not know which query in SQL to solve it. If you understand it, you can give me solution. thanks very much!

Homework?

http://www.w3schools.com/sql/sql_union.asp

BTW
Poor database design often leaves problems when trying to extract data from several tables.

A third table is required for the cities, then the city field in the other two tables should be a refrence to the ID of the entry in the city table.
That would make queries much simpler.