- A Table record in first table is related to more than one record of second table. But second table record maps to only one entry of first table
- NocoDB refers to this category of relationship as **has many**
- For every **has many** relation defined, NocoDB augments **belongs to** relationship column in the adjacent table automatically
- Example: Country **has many** Cities. (other way mapping > City **belongs to** Country )
- Many to many
- A Table record in first table is related to more than one record of second table; second table record can also map to more than on record of first table.
- NocoDB refers to this category of relationship as **many to many**
- For every **many to many** relation defined between tables, NocoDB augments **many to many** relationship column in the other table automatically
- Example: Film **has many** Actors. Actor **has many** Films (works on many films)
Further details of relationship types can be found [here](https://afteracademy.com/blog/what-are-the-different-types-of-relationships-in-dbms)
It is important to note that, earlier supported column type **LinkToAnotherRecord** for creating relations is considered deprecated. While the old datatype is still supported for backward compatibility, it is no longer possible to create new fields of that type.
The main distinction between these two column types lies in how the contents are displayed within the cell when links are established between two tables. With the **LinkToAnotherRecord** column type, the cell displays the **Primary value** of the related records. On the other hand, the **Links** column type only shows the **count** of related records.
The decision to switch over to new column type was made to ensure better performance and scalability of the application, more so when the records & the number of records in the related table is large.
Child list to display the related records can be accessed by clicking on the link count displayed on the cell.
Except for the column type, the following procedures remain same as before
- Create, update & delete a relationship column,
- Link & unlink a record,
- Create a lookup and rollup columns
Workflow details are captured below.
## Adding a relationship
1. Create column
Click on '+' button at end of column headers
2. Update column name
Input name in the text box provided
3. Select column type
Select Column type as "Links" from the drop-down menu
4. Choose relationship type
- 'Has Many' corresponds to the 'One-to-many' relationships
- 'Many To Many' corresponds to the 'Many-to-many' relationships
5. Select child table from drop down menu
6. Click on 'Save'
A new column will get created in both the parent table & child table
## Linking records
### 1. Open link record tab
Click on the '+' icon in corresponding row - cell
### 2. Select from the option displayed
Use 'Filter box' to narrow down on search items.
You can opt to insert a new record as well, using "+ New Record" button.
You can use `ALT + Click` to insert multiple options together.
### 3. Column display for "Has Many" relationship
Country 'has many' City
### 4. Column display for "Belongs to" relationship [Automatically updated]
City 'belongs to' Country.
Note: Primary value is still used as cell display value for "Belongs to" as it can have only one associated record.
## Unlinking records
1. Click on link count to open Child modal
2. Click on Unlink icon against required item
## Link label reconfiguration
Use column edit menu for **Links** to reconfigure display label
