How to join 3 or more tables in SQL
In a database, information is typically separated into different tables. The JOIN (or INNER JOIN) statement enables us to combine the columns we require into a single table. The syntax of joining 3 or more tables is the same as joining 2 tables:
JOIN,INNER JOINand,can be used to join tables. However, if a,is used, then theWHEREclause needs to be used instead of theONclause.
1. Simple Join
First, all the tables are joined using the JOIN keyword, then the WHERE clause is used:
FROM Employee e JOIN Salary s JOIN Department d
WHERE e.ID = s.Emp_ID AND e.Dep_ID = d.ID
2. Nested Join
The nested JOIN statement is used with the ON keyword:
SELECT e.ID, e.Name, s.Salary, d.Name
FROM (Employee e JOIN Salary s ON e.ID = s.Emp_ID)
JOIN Department d ON e.Dep_ID = d.ID
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Different types of SQL joins
Understand the different types of SQL joins used for combining data from multiple tables.What is inner join in SQL?
Learn how inner joins return matched rows from both tables in SQL.What is outer join in SQL?
Explore outer joins and how they return unmatched rows as well.What is a self join in SQL?
Discover how self joins allow a table to join with itself.What is a natural join in SQL?
Learn how natural joins match columns with the same name in SQL tables.What is a hash join in SQL?
Understand hash joins, which are used for large-scale data matching and combining.What is the SQL CROSS JOIN?
Explore the SQL CROSS JOIN to combine every row from one table with every row from another.What is an equi join in SQL?
Learn how equi joins match rows based on the equality of values between tables.How to join 3 or more tables in SQL
Master the technique of joining multiple tables in a SQL query for complex data retrieval.
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