Data Query Lanage(DQL): Multiple Table Search-Join && Union

JOIN

Combine rows from two or more tables

SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;

1. Inner Join return records that have matching values in both tables A union B
2. Left Join return all records from the left table, and the matched records from the right table A
3. Right Join return all records from the right table and the matched records from the left table B
4. FULL Join return all records when there is a match in either left or right table AUB

UNION

Combine result from multiple SELECT statements

1. Each SELECT statement must have same account of columns
2. The columns must also have similiar data types.
3. The columns in each SELECT statement must also be in the same order

   SELECT 'Customer' As Type, ContactName, City, Country
   FROM Customers
   UNION
   SELECT 'Supplier', ContactName, City, Country
   FROM Suppliers;