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This article mainly introduces what is the primary key in MySQL, which can be used for reference by friends who need it. I hope you will learn a lot after reading this article. Next, let the editor take you to learn about it.

Adding a primary key to all tables is a good habit to use a database, and the primary key will help users avoid introducing duplicate data problems when migrating data.

What is the primary key?

Each row in the table is uniquely determined by the primary key (contention). When you create a table, you must specify the columns that make up the primary key, which are called primary key columns. Primary key column must have a value. You must ensure that the combination of the values of the primary key column uniquely determines a row. The type of primary key column cannot be changed during subsequent use.

Take HybridDB for MySQL as an example:

There is no sharing between logical partitions of HybridDB for MySQL, so uniqueness can be guaranteed within partitions, but all database and table constraints, even including uniqueness constraints, cannot be maintained between partitions.

Global uniqueness is guaranteed by using the AUTO_INCREMENT column.

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