> For the complete documentation index, see [llms.txt](https://docs.tableplus.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tableplus.com/gui-tools/working-with-table/constraint.md).

# Constraint

## **NOT NULL Constraint**

You can specify a NOT NULL constraint on a column from the Table Structure view:

* Open the table structure view (**`⌘ + ^ + ]`**)
* Specify the value of the **`is_nullable`** field to:
  * **`YES`** to add NOT NULL constraint.
  * **`NO`** to remove the NOT NULL constraint.
* Press **`⌘ + S`** to commit changes to the server.

![](/files/-LsTTOqltm4z4bKIW91d)

## **PRIMARY KEY** Constraint

You can specify a Primary Key Constraint on a column from the Table Structure view:

* Open the table structure view (**`⌘ + ^ + ]`**)
* Specify the value in the Primary Key box:
  * Add the column name into the Primary Key box to make it a define the Primary Key Constraint on that column.
  * Delete the column name from the Primary Key box to remove the Primary Key Constraint on that column.
* Press **`⌘ + S`** to commit changes to the server.

![](/files/-LsTVZHK7ICUzSlnNt4f)

## FOREIGN KEY **constraint**

You can specify a Foreign Key Constraint on a column from the Table Structure view:

* Open the table structure view (**`⌘ + ^ + ]`**)
* Click on the **`foreign_key`** field and choose **`Create a foreign key on column`**
* From the popup, specify the foreign relationship.
* Press **`⌘ + S`** to commit changes to the server.

![](/files/-LsTWtkpXXLoL7kq7Arw)

## DEFAULT Constraint

You can specify a default value for a column from the Table Structure view:

* Open the table structure view (**`⌘ + ^ + ]`**)
* Specify the default value in the **`column_default`** field. It's **`NULL`** by default.
* Press **`⌘ + S`** to commit changes to the server.