Depending on the desired output, we can make use of the different joins. The duplicate values are removed by default in SQL UNION To use SQL JOINS the two given tables need to have at. Lets look at a selection from the 'Orders' table: Then, look at a selection from the 'Customers' table: Notice that the 'CustomerID' column in the 'Orders' table refers to the 'CustomerID' in the 'Customers' table. The duplicate values can exist in SQL JOINS. SQL provides us with multiple types of JOINs- INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN. A JOIN clause is used to combine rows from two or more tables, based on a related column between them. If you use some aggregate function or add a new column by some calculation or concatenation, the new column will appear in the result. Note that, if the first table consists of two columns and the second table consists of three columns, then the result might contain more than five columns as well. Here, the student id in both tables shows the relation between them. For example, the student table consists of the student id which is further used in the marks table to store the marks of each student. Also, there must be a relation between the tables before using the JOIN. When you use the JOIN to combine the data from two or multiple tables, the result will consist of new columns. Example Here is an example of a MySQL INNER JOIN: SELECT suppliers.supplierid, suppliers.suppliername, orders.orderdate FROM suppliers INNER JOIN orders ON suppliers.supplierid orders. To keep the duplicate records, you can use the UNION ALL. The use of other functions is needed to remove the duplication. UNION must need the result set to have similar numbers of columns and of the same data type. JOIN need not the tables to have the same number of columns and of the same data type. Union combines the result of two or more select queries. It combines the two result-set into new rows. JOIN combines the data from multiple tables based on the relation between them. It combines the two tables into new columns. ![]() JOIN combines the data from multiple tables based on the relation between them. Now let’s see some important differences between JOIN and UNION quickly.
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