SQL select statements with multiple tables

• When working with relational databases, data is usually spread across multiple tables to avoid redundancy and ensure normalization. To get meaningful results, you often need to query data from more than one table. This is where SQL SELECT statements with multiple tables come into play.
  
• Common Ways to Use SELECT with Multiple Tables:
  
• INNER JOIN
  

 Returns only the rows that have matching values in both tables.

 SELECT employees.name, departments.dept_name

FROM employees

INNER JOIN departments ON employees.dept_id = departments.id;

 This retrieves employees along with their department names.

• LEFT JOIN (or LEFT OUTER JOIN)
  
•  Returns all rows from the left table, even if there’s no match in the right table. Useful when you want all employees, even those not assigned to a department.
  
• RIGHT JOIN (or RIGHT OUTER JOIN)
  
•  Similar to LEFT JOIN but returns all rows from the right table.
  
• FULL OUTER JOIN
  
•  Returns rows when there is a match in either table, including unmatched rows from both sides.
  
• CROSS JOIN
  
•  Produces the Cartesian product of both tables, pairing each row from one with every row from the other.
  
• Using Aliases
  
•  Aliases simplify queries and make them more readable when dealing with multiple tables.
  

Key Points:

• Use JOINs to connect related data across tables.
  
• INNER JOIN is most common, while LEFT/RIGHT JOIN ensures unmatched rows aren’t lost.
  
• Always use proper conditions (ON clause) to avoid unexpected results.
  

In short, SQL SELECT with multiple tables lets you combine and analyze related data efficiently, giving you more complete insights from your database.