> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/architecture/server-constraints.md).

# Server Constraints

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{% column %}
{% content-ref url="/pages/5TBe9CxJOF9ArTGcFRQN" %}
[Server Constraints Overview](/docs/server/architecture/server-constraints/server-constraints-overview.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Provides a high-level overview of how MariaDB Server enforces data integrity through various architectural constraint types.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/cFxjWF5fTZLP1SZzW8SQ" %}
[AUTO\_INCREMENT Constraints](/docs/server/architecture/server-constraints/auto_increment-constraints.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Explains the limitations and behavior of `AUTO_INCREMENT` columns, including how they handle maximum values and gaps in sequences.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/frdXkOf4PaYrzWTccOmR" %}
[FOREIGN KEY Constraints](/docs/server/architecture/server-constraints/foreign-key-constraints.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Details the requirements and limitations for defining foreign keys to ensure referential integrity between tables.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/JQVhrdu6QF8M04rjsgFn" %}
[NOT NULL Constraints](/docs/server/architecture/server-constraints/not-null-constraints.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Describes how `NOT NULL` constraints prevent `NULL` values from being stored in specific columns.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/T1jDxKqBqLYEn4pyiOmd" %}
[PRIMARY KEY Constraints](/docs/server/architecture/server-constraints/primary-key-constraints.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Outlines the rules for primary keys, which uniquely identify each record in a table and cannot contain `NULL` values.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/UfoCAjXIfk1NNMljj61A" %}
[UNIQUE Constraints](/docs/server/architecture/server-constraints/unique-constraints-with-mariadb-enterprise-server.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Explains the specific implementation and considerations for unique constraints when using MariaDB Enterprise Server.
{% endcolumn %}
{% endcolumns %}