Documentation Home
MySQL 5.7 Reference Manual
Related Documentation Download this Manual
PDF (US Ltr) - 33.9Mb
PDF (A4) - 34.0Mb
PDF (RPM) - 33.2Mb
EPUB - 8.5Mb
HTML Download (TGZ) - 8.2Mb
HTML Download (Zip) - 8.2Mb
HTML Download (RPM) - 7.1Mb
Eclipse Doc Plugin (TGZ) - 9.0Mb
Eclipse Doc Plugin (Zip) - 11.1Mb
Man Pages (TGZ) - 219.4Kb
Man Pages (Zip) - 322.3Kb
Info (Gzip) - 3.2Mb
Info (Zip) - 3.2Mb
Excerpts from this Manual

MySQL 5.7 Reference Manual  /  ...  /  Using Primary Keys

8.3.2 Using Primary Keys

The primary key for a table represents the column or set of columns that you use in your most vital queries. It has an associated index, for fast query performance. Query performance benefits from the NOT NULL optimization, because it cannot include any NULL values. With the InnoDB storage engine, the table data is physically organized to do ultra-fast lookups and sorts based on the primary key column or columns.

If your table is big and important, but does not have an obvious column or set of columns to use as a primary key, you might create a separate column with auto-increment values to use as the primary key. These unique IDs can serve as pointers to corresponding rows in other tables when you join tables using foreign keys.


User Comments
Sign Up Login You must be logged in to post a comment.