### 15.1.2 Best Practices for InnoDB Tables

 This section describes best practices when using `InnoDB` tables.

* Specify a primary key for every table using the most frequently queried column or columns, or an auto-increment value if there is no obvious primary key.

* Use joins wherever data is pulled from multiple tables based on identical ID values from those tables. For fast join performance, define foreign keys on the join columns, and declare those columns with the same data type in each table. Adding foreign keys ensures that referenced columns are indexed, which can improve performance. Foreign keys also propagate deletes and updates to all affected tables, and prevent insertion of data in a child table if the corresponding IDs are not present in the parent table.

* Turn off autocommit. Committing hundreds of times a second puts a cap on performance (limited by the write speed of your storage device).

* Group sets of related DML operations into transactions by bracketing them with `START TRANSACTION` and `COMMIT` statements. While you don't want to commit too often, you also don't want to issue huge batches of [`INSERT`](insert.html), [`UPDATE`](update.html), or [`DELETE`](delete.html) statements that run for hours without committing.

* Do not use [`LOCK TABLES`](lock-tables.html) statements. `InnoDB` can handle multiple sessions all reading and writing to the same table at once without sacrificing reliability or high performance. To get exclusive write access to a set of rows, use the [`SELECT ... FOR UPDATE`](innodb-locking-reads.html) syntax to lock just the rows you intend to update.

* Enable the [`innodb_file_per_table`](innodb-parameters.html#sysvar_innodb_file_per_table) variable or use general tablespaces to put the data and indexes for tables into separate files instead of the system tablespace. The [`innodb_file_per_table`](innodb-parameters.html#sysvar_innodb_file_per_table) variable is enabled by default.

* Evaluate whether your data and access patterns benefit from the `InnoDB` table or page compression features. You can compress `InnoDB` tables without sacrificing read/write capability.

* Run the server with the [`--sql_mode=NO_ENGINE_SUBSTITUTION`](server-system-variables.html#sysvar_sql_mode) option to prevent tables from being created with storage engines that you do not want to use.

