JOINS IN SQL INTRO

SQL JOINS

SQL Joins are used to combine data from two or more tables based on a related column. They help in:

• Retrieving connected data stored across multiple tables.
• Matching records using common columns.
• Improving data analysis by combining related information.
• Creating meaningful result sets from separate tables.

Types of SQL Joins

SQL joins are categorized into different types based on how rows from two tables are matched and combined.

INNER JOIN

INNER JOIN is used to retrieve rows where matching values exist in both tables. It helps in:

• Combining records based on a related column.
• Returning only matching rows from both tables.
• Excluding non-matching.
• Ensuring accurate data relationships between tables.

LEFT JOIN

LEFT JOIN is used to retrieve all rows from the left table and matching rows from the right table. It helps in:

• Returning all records from the left table.
• Showing matching data from the right table.
• Displaying NULL values where no match exists in the right table.
• Performing outer joins, also known as LEFT OUTER JOIN.

RIGHT JOIN

RIGHT JOIN is used to retrieve all rows from the right table and the matching rows from the left table. It helps in:

• Returning all records from the right-side table.
• Showing matching data from the left-side table.
• Displaying NULL values where no match exists in the left table.
• Performing outer joins, also known as RIGHT OUTER JOIN.

FULL JOIN

FULL JOIN is used to combine the results of both LEFT JOIN and RIGHT JOIN. It helps in:

• Returning all rows from both tables.
• Showing matching records from each table.
• Displaying NULL values where no match exists in either table.
• Providing complete data from both sides of the join.
• Returning all rows from the same table.
• Used to compare deferent tables from same sable.
• Used to find duplicate records.

SELF JOIN

SELF JOIN is used to join a table with it self. It helps in:

• Returning all rows from the same table.
• Used to compare different records from same table.
• Used to find duplicate records.