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Questions and Answers
Which type of JOIN returns all records when there is a match in either left or right table?
Which type of JOIN returns all records when there is a match in either left or right table?
- INNER JOIN
- RIGHT (OUTER) JOIN
- LEFT (OUTER) JOIN
- FULL (OUTER) JOIN (correct)
What is the purpose of a JOIN clause in SQL?
What is the purpose of a JOIN clause in SQL?
- To delete rows from a table
- To combine rows from two or more tables based on a related column between them (correct)
- To update rows in a table
- To create new tables
Which type of JOIN returns all records from the left table and the matched records from the right table?
Which type of JOIN returns all records from the left table and the matched records from the right table?
- RIGHT (OUTER) JOIN
- FULL (OUTER) JOIN
- INNER JOIN
- LEFT (OUTER) JOIN (correct)
What is the output of the following SQL statement: SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate FROM Orders INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;?
What is the output of the following SQL statement: SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate FROM Orders INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;?
What type of JOIN returns only records that have matching values in both tables?
What type of JOIN returns only records that have matching values in both tables?
What is the difference between a LEFT JOIN and a RIGHT JOIN?
What is the difference between a LEFT JOIN and a RIGHT JOIN?
What is the purpose of a JOIN clause in SQL?
What is the purpose of a JOIN clause in SQL?
What is the output of the following SQL statement: SELECT Orders.OrderID, Customers.CustomerName FROM Orders LEFT JOIN Customers ON Orders.CustomerID=Customers.CustomerID;?
What is the output of the following SQL statement: SELECT Orders.OrderID, Customers.CustomerName FROM Orders LEFT JOIN Customers ON Orders.CustomerID=Customers.CustomerID;?
What type of JOIN returns all records when there is a match in either left or right table?
What type of JOIN returns all records when there is a match in either left or right table?
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Study Notes
SQL JOIN Types and Functions
- FULL OUTER JOIN: Returns all records when there is a match in either the left table or the right table, including unmatched rows.
- Purpose of JOIN Clause: Combines rows from two or more tables based on a related column, allowing for comprehensive data analysis from multiple sources.
Specific JOIN Types
- LEFT JOIN (LEFT OUTER JOIN): Returns all records from the left table and the matched records from the right table. If no match exists, NULL values are returned for the right table's columns.
- INNER JOIN: Selects only records with matching values in both tables. Data is returned only for entries where there is a match.
- RIGHT JOIN (RIGHT OUTER JOIN): Similar to LEFT JOIN, but returns all records from the right table and matched records from the left, with NULL values for non-matching left records.
Output and Examples of SQL Statements
- SQL Output for INNER JOIN: The query
SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate FROM Orders INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;retrieves OrderID, CustomerName, and OrderDate for orders with matching customer records. Non-matching entries are excluded. - SQL Output for LEFT JOIN: The query
SELECT Orders.OrderID, Customers.CustomerName FROM Orders LEFT JOIN Customers ON Orders.CustomerID=Customers.CustomerID;returns OrderID and CustomerName, including all orders regardless of whether a match exists in the Customers table. Non-matching customers will show NULL for CustomerName.
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