How to Correctly Perform Inner Joins on Multiple SQL Tables?

Inner Joining Multiple Tables in SQL

An inner join is an SQL operation that combines rows from multiple tables based on a common column value, returning only those rows where the condition is met. When working with more than two tables, it is essential to specify the join criteria for each pair of tables.

In your given code, you were attempting to inner join three tables using a single foreign key with the following syntax:

SELECT * 
FROM table1 
INNER JOIN table2
INNER JOIN table3 
ON table1.primaryKey=table2.table1Id=table3.table1Id

This query will not return any results because the join criteria is incorrect. To correctly join multiple tables, you need to specify the join condition for each table pair separately. The correct syntax for inner joining three tables with the same foreign key is:

SELECT * 
FROM table1 
INNER JOIN table2
      ON table1.primaryKey=table2.table1Id
INNER JOIN table3
      ON table1.primaryKey=table3.table1Id

In this corrected query, the join criteria for each table pair (table1 and table2, table1 and table3) are explicitly specified, ensuring that only rows with matching foreign key values from all three tables are returned.

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