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Database

Database. Week 5 SQL basics JOIN, ALIAS. JOIN. SQL joins are used to query data from two or more tables, based on a relationship between certain columns in these tables. JOIN(or INNER JOIN) : Return rows when there is at least one match in both tables

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Database

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  1. Database Week 5 SQL basics JOIN, ALIAS Fox MIS Spring 2011

  2. JOIN • SQL joins are used to query data from two or more tables, based on a relationship between certain columns in these tables. • JOIN(or INNER JOIN): Return rows when there is at least one match in both tables • LEFT JOIN: Return all rows from the left table, even if there are no matches in the right table • RIGHT JOIN: Return all rows from the right table, even if there are no matches in the left table • FULL JOIN: Return rows when there is a match in one of the tables

  3. INNER JOIN • SELECT column_name(s)FROM table_name1INNER JOIN table_name2ON table_name1.column_name=table_name2.column_name • SELECT Persons.LastName, Persons.FirstName, Orders.OrderNoFROM PersonsINNER JOIN OrdersON Persons.P_Id=Orders.P_IdORDER BY Persons.LastName • JOIN(or INNER JOIN): Return rows when there is at least one match in both tables

  4. Non-standard, but Common syntax • SELECT Persons.LastName, Persons.FirstName, Orders.OrderNoFROM PersonsINNER JOIN OrdersON Persons.P_Id=Orders.P_Id • SELECT Persons.LastName, Persons.FirstName, Orders.OrderNoFROM Persons, OrdersWHERE Persons.P_Id=Orders.P_Id • Above two will return the same results.

  5. Example • Database: Sakila, Table: Customer and Customer_list • Customer table manages customer’s first name and last name in separate fields, while customer_list table keeps them in one field. • Task: Make the list of customer id, customer name, their email addresses, and their active statuses. Sort them by customer id.

  6. ALIAS • SELECT column_name(s)FROM table_nameAS alias_name • SELECT column_name AS alias_nameFROM table_name • You can give a table or a column another name by using an alias • SELECT po.OrderID, p.LastName, p.FirstNameFROM Persons AS p, Product_Orders AS poWHERE p.LastName='Hansen' AND p.FirstName='Ola‘ • SELECT Product_Orders.OrderID, Persons.LastName, Persons.FirstNameFROM Persons, Product_OrdersWHERE Persons.LastName='Hansen' AND Persons.FirstName='Ola'

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