NESTED LOOP OUTER
Short Description
A nested loops join reads rows from source A and for each row, scans source B, returning matching rows.
Detailed Description​
The NESTED LOOP join is in OLTP systems to join small tables. Ideally the column used for the join on the second table should be indexed to stop repeated table scans of the second table.
Further Reading​
- Oracle Magazine - How to read an execution plan
- Oracle Tuning Guide - Explaining and Displaying Execution Plans
- Oracle Tuning Guide - Comparing Execution Plans Tutorial
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