I will explain SQL Cartesian Product in this post.
SQL Cartesian Product
SQL Cartesian Product is used when any join conditions don’t exist between tables. Cartesian product is created between two data sources, and Optimizer joins every row from one source with every row from the other data source as follows.
- Cartesian product is mentioned, in case of where the join condition between two tables is not defined.
- It fetchs all records from the table on the right for each record of the table on the left.
For example; hr.regions and hr.locations will be used in the cartesian product as follows.
SELECT COUNT(*) FROM hr.regions ; SELECT COUNT(*) FROM hr.locations ;
SELECT * FROM hr.regions, hr.locations;
HR.REGIONS has 4 row and HR.LOCATIONS has 23 rows, when you did the cartesian product between these two tables, result will be 4×23 = 92 rows like above.
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