Understanding Natural Join in SQL for Effective Banking Data Management
Note: All SQL queries used in the Case study is tested on Oracle,SQLServer,MySQL and PostgreSQL.
1.Show all customer and account details where the natural relationship between the two tables is based on CustomerID.
SELECT *
FROM Customers
NATURAL JOIN Accounts;
Explanation
It uses a NATURAL JOIN to retrieve information about the customers and accounts found in the Customers table and Accounts table via their natural relationship across the column named CustomerID. A NATURAL JOIN automatically identifies which columns in one table have like names in the other table and performs the join based upon those columns:. Because both of these tables merely coincidentally have a column named CustomerID, joining will only return records where the CustomerID matches in both tables. This result set will contain all columns from both the Customers and Accounts tables for all customers who have one or more accounts associated. This does not provide an explicit join condition; thus the syntax is reduced rather elegantly in a query concerning accessing information for a customer with account details. However, care is necessary when using NATURAL JOIN because if there exist multiple columns of the same name which should not be joined at all, it will result in unexpected results. Overall, it is a very simple and obvious relationship to model customeraccount relationships in a relational database.
2.List all transactions and account details naturally linked by AccountID.
SELECT *
FROM Transactions
NATURAL JOIN Accounts;
Explanation
This SQL statement employs NATURAL JOIN to retrieve all transaction records and associated account information from the Transactions and Accounts tables. Thus, by using NATURAL JOIN, the column that is common in both tables and named AccountID will be automatically recognized so the join will actually occur based on that common column. Of course, this means that the output will contain all columns from both the Transactions and Accounts tables for all transactions associated with the account. To put it another way, for each transaction the query returns account type and balance information associated with the details of the transaction itself including amount and date. NATURAL JOIN makes the syntax of a query so simplistic that it is no longer necessary to make explicit a join condition and the relation between the transactions and accounts could be written with considerably less words. On the other hand, while using NATURAL JOIN one has to be careful about the outcome because it may produce some output which one is not initially interested in getting if columns of the same name appear across the tables which are not intended to be joined. This query effortlessly combines transactional data with account information in a relational database environment.
3.Retrieve customer names and their account balances using a natural join.
SELECT Name, Balance
FROM Customers
NATURAL JOIN Accounts;
Explanation
This query selects the column Name in the Customers table and the column Balance in the Accounts table.The NATURAL JOIN would allow you to naturally combine the two tables based on the common column here being CustomerID so you can fetch the corresponding names of the customers with their respective account balances in one single result set.
This query is compatible for Oracle,MySQL,SQLServer,postgreSQL.
4.Find customer names and transaction amounts naturally connected by account ownership.
SELECT Name, Amount
FROM Customers
NATURAL JOIN Accounts
NATURAL JOIN Transactions;
Explanation
This SQL query retrieves customer names and transaction amounts with the help of a NATURAL JOIN of three tables: Customers, Accounts, and Transactions. It joins the Customers table to the Accounts table by their common column CustomerID linking customers to their respective accounts.
Then it carries out another NATURAL JOIN with the Transactions table through the column AccountID which relates accounts to their transactions. This means that at the output stage a list of customer names combined with their transaction amounts will appear.
This form saves a lot of time when seeking the relationship between customers and their activities in terms of transactions since one need not to type in the joining conditions instead the NATURAL JOIN automatically links columns of the same name found in the tables involved. The query is compatible across Oracle, MySQL, PostgreSQL, and SQL Server thus versatile to use in different environments of a database.
5.Display all customer and transaction types naturally linked through accounts for saving and current.
SELECT *
FROM Customers
NATURAL JOIN Accounts
NATURAL JOIN Transactions
WHERE AccountType IN ('Savings', 'Current');
Explanation
Query Fetches all the information about customers together with the types of transactions in a NATURAL JOIN on three tables, namely, Customers, Accounts, and Transactions.
The question begins with a NATURAL JOIN of Customers and Accounts on the common column CustomerID.
Then another NATURAL JOIN occurs this time between it and the table Transactions with a common column AccountID.
It will return the result set for all columns of customers whose accounts are of type 'Savings' or 'Current' just as they are named in the WHERE clause. NATURAL JOIN identifies common columns and automatically performs joins without defining the join condition explicitly. This will then enable a complete description of the customers with their type of transactions thereby simplifying the analysis of the activities on customer's savings and current accounts.
It is cross compatible with Oracle, MySQL, PostgreSQL, and SQL Server that makes it very flexible to use in multiple database scenarios.
Advantages of Natural JOIN in SQL
Simplifies Data Retrieval
A natural join automatically matches columns that have the same name in each of the tables to combine data related in an easier way without references of the columns.
Reduces Redundancy
The combination of tables on matching columns in one table with the other through natural joins also helps to reduce data duplication thereby creating cleaner data sets.
Improves Query Readability
Natural language joins are typically shorter and also easier to read. Therefore, anyone is able to easily understand how the different data in the tables is being combined.
Enhances Data Integrity
Only natural joins combine rows with matching values in those columns that have been specified. This eliminates possibilities of inaccuracies in data being pulled together.
Streamlines Data Management
For very large databases natural join is much easier and faster to deal with/analyse even data, specifically when it is applied in applications such as banks where several other tables need to be involved.
When to Use Natural JOIN ?
Common Columns
You can employ natural join if you have your two tables and they share columns of the same names. It is rather handy to join related data without knowing in advance which columns to join.
Quick and Easy Queries
If you need to write your SQL queries fast, then natural joins will surely assist because they automatically match columns for you, thereby making your code short and manageable.
Avoiding Duplicates
Natural Join in Case You Need to Join Data Without Duplicate Columns in the Output Natural joins are good selections whenever you need to join data such that the columns of the output have not been duplicated. They make sure that you get only unique information from the tables.
Clear Data Relationships
Use a natural join when working with an organized database with clear relationships among the tables. This ensures that the information being pulled together is correct.
Readable SQL
Natural Joins may help you in case you want your SQL queries clean and easily readable. They reduce the amount of the code that has to be written from this point and it is easier to understand which tables are interconnected.
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Other Topics for Account Management
Cross Join
Joins With Group by Having
Inner join Banking case study
Joins with Subqueries
Outer Join
