Grokking SQL for Tech Interviews
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Introduction
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SQL Joins helps you when you need to combine data from different tables in a database. They bring together data from different tables based on a common attribute, creating a seamless connection between them.

Types of SQL JOINS

Following are the main types of SQL Joins. In the next sections, we'll thoroughly explore the main types of SQL Joins, offering a detailed understanding of their functions.

  • INNER JOIN fetches rows where there is a match in both tables based on a specified condition. It's straightforward and effective, just like finding your perfect match.
  • LEFT JOIN fetches all rows from the left table and matching rows from the right table. If there's no match, the result will show NULL values for the right table columns.
  • RIGHT JOIN focuses on the right table, ensuring that all rows from the right table are included, along with matching rows from the left table.
  • FULL OUTER JOIN is the ultimate gathering, showcasing all rows from both tables, with matches displayed where they occur and NULL values where there's no match. It's like bringing everyone together for a grand reunion.
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Special Types of SQL JOINS

Here are some special types of SQL Joins.

  • Self Join is a peculiar type of join where a table is joined with itself. It is useful when you want to compare or combine rows within the same table. Aliases are commonly used to distinguish between the two instances of the same table.
  • Equi Join is a type of join in SQL that combines rows from two or more tables based on the equality of values in specified columns. Unlike a regular INNER JOIN, which can use any condition for matching, an Equi Join specifically uses the equality operator (=) to match values between the joined columns.
  • Natural Join is a join operation in SQL that automatically matches columns with the same name in both tables. In other words, it relies on the commonality of column names to establish the join condition. While it offers a convenient way to join tables, it's essential to use Natural Joins cautiously, as it may lead to unintended matches if the column names are not unique or if changes occur in the table structure.

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