# BigQuery Best Practices

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### Cost Reduction

* Avoid using `SELECT *`
* Price your queries before running them
* Use clustered or partitioned tables
* Use streaming inserts with caution
* Materialize query results in stages

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### Query Performance

* Filter of partitioned or clustered column

* Try denormalizing data
  * Use nested or repeated columns in case you have a complicated structure

* Use external data sources appropriately
  * It might incur more costs if 

* Reduce data before using a JOIN

* Do not treat WITH clauses as prepared statements

* Avoid oversharding tables

* Avoid JavaScript user-defined functions

* Use approximate aggregation functions (HyperLogLog++)

* Order Last, 

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