SQL Queries

[churchill]

Help Me Please

Hi i wondered if anyone could help me. Im creating a large database and i have come accross a few problems which trying to create SQL queries. i wondered if anyone was an expert at them they could assist me.
Thanks

 

[Smart]

What are you trying to do.
The more info you supply the better the chance of some one being to help you

 

[churchill]

Explanation

i have a customer database made up of 19 tables. i need each table as each tables displays different sales data for different product groups. from the 19 tables i have created a list of customers, with an SQL Query. I need to know be able to search for any list of customer who are linked to any three tables, what ever my boss whiches to do.

i am also looking into a way to sort data, i have another sales database at the moment we match manually from simple queries. im looking for the system to compare all the data entered into the and find its match, so i want it to match by the id code and product so i no that it is a match.

Can you help