Inner JOIN vs Outer JOIN: Difference and Comparison

Key Takeaways

  1. An inner join combines rows from two or more tables based on a specified condition.
  2. Outer join is a more flexible join type that retrieves all rows from one of the tables.
  3. Inner join performs faster as it only involves matching rows from both tables. In contrast, outer join might be slower,  as it includes unmatched rows.

What is an Inner Join?

An inner join combines rows from two or more tables based on a specified condition, called a joint predicate. The result set of an inner join contains the rows with matching values in both tables involved.

It is a fundamental and powerful tool that enables data professionals to combine information from multiple tables precisely. This join type allows them to extract relevant data by establishing relationships between tables based on standard columns.

The beauty of inner join lies in its ability to filter out irrelevant information and focus solely on data directly related to the given criteria. Its ability to combine data accurately based on common attributes opens a wide range of possibilities for analyzing relationships within relational databases.

What is an Outer Join?

An outer join is a more flexible join type that retrieves all rows from at least one of the tables, even if there are no matching values in the other table. It preserved the unmatched rows by replacing missing values with Null in the result set for the non-matching side of the join.

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There are three types of outer join- left outer join, right outer join and full outer join. It broadens the scope of data analysis by including non-matching records. This unique characteristic empowers data professionals to quickly uncover valuable insights, identify gaps, and navigate complex datasets.

 With this tool, businesses can harness the full potential of their data, leading to better decision-making, improved performances and enhanced insights that drive growth and success.

Difference Between Inner Join and Outer Join

  1. Inner join returns only the matching rows from both tables based on the specified condition, while outer join returns matching rows from both tables and includes non-matching rows with null values for the columns from the table with no match.
  2. Inner join produces a result set containing only the common records from both tables. In contrast, the outer join has a result set containing common records and unmatched rows from one or both tables.
  3. Inner join performs faster as it only involves matching rows from both tables. In contrast, outer join might be slower, especially when dealing with large datasets, as it includes unmatched rows.
  4. Inner join retrieves data from two or more related tables where a match is required in both tables. In comparison, outer join retrieves data from two or more related tables, including unmatched records, for analysis.
  5. Inner join returns fewer rows than the original table since it includes only matched rows. An outer join returns more rows than the actual tables, as it has unmatched rows with null values.

Comparison Between Inner Join and Outer Join

ParametersInner joinOuter join
DefinitionReturns only the matching rows from both tablesReturns matching rows from both tables and include non-matching rows with null values for the columns.
Result setContains common records from both tablesHas common records and unmatched rows from one or both tables
PerformanceFasterSlower
UsageTo retrieve data from two or more related tables where a match is required in both tablesTo retrieve data from two or more related tables, including unmatched records
Number of rowsFewerMore
References
  1. https://dl.acm.org/doi/abs/10.1145/128762.128764
  2. https://scholar.ppu.edu/handle/123456789/8270
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Last Updated : 14 October, 2023

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