Challenge: Comparing Query Plans
When working with SQL databases, understanding how different queries are executed is essential for optimizing performance. The EXPLAIN command is a powerful tool that reveals the query plan chosen by the database engine. By comparing the plans for similar queries, you can identify which approach is more efficient and why. In this challenge, you will analyze and compare the EXPLAIN output for two queries: one that selects all rows from the customers table, and another that filters results using a WHERE clause on an indexed column.
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Compare the EXPLAIN plans for two queries against the customers table. The first query selects all rows without any filtering, while the second query selects rows where customer_id matches a specific value. Both queries use the same table, but only the second query filters on the primary key column, which is indexed.
- Review the
EXPLAINoutput for both queries. - Identify which query is more efficient.
- Explain why the query with the
WHEREclause oncustomer_idis more efficient, referencing the use of the index and the number of rows scanned.
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When working with SQL databases, understanding how different queries are executed is essential for optimizing performance. The EXPLAIN command is a powerful tool that reveals the query plan chosen by the database engine. By comparing the plans for similar queries, you can identify which approach is more efficient and why. In this challenge, you will analyze and compare the EXPLAIN output for two queries: one that selects all rows from the customers table, and another that filters results using a WHERE clause on an indexed column.
Swipe to start coding
Compare the EXPLAIN plans for two queries against the customers table. The first query selects all rows without any filtering, while the second query selects rows where customer_id matches a specific value. Both queries use the same table, but only the second query filters on the primary key column, which is indexed.
- Review the
EXPLAINoutput for both queries. - Identify which query is more efficient.
- Explain why the query with the
WHEREclause oncustomer_idis more efficient, referencing the use of the index and the number of rows scanned.
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