nocodb/packages/noco-docs/versioned_docs/version-0.109.7/030.setup-and-usages/100.primary-key.md

title	description
Primary Key	Understanding Primary Key in NocoDB!

What is a Primary Key ?

• A primary key is a special database table column designated to uniquely identify each table record.

What is the use of Primary Key ?

• As it uniquely identifies an individual record of a table, it is used internally by NocoDB for all operations associated with a record

Primary Key in NocoDB

• Primary Key that gets defined / used in NocoDB depends on how underlying table was created. Summary is captured below

1. From UI, Create new table / Import from Excel / Import from CSV
   1. An ID [datatype: Integer] system field created by default during table creation is used as primary key
   2. Additional system fields created-at, updated-at are inserted by default & can be omitted optionally; these fields can be deleted after table creation
2. Connect to existing external database
   1. Existing primary key field defined for a table is retained as is; NocoDB doesn't insert a new ID field
   2. Additional system fields created-at, updated-at are not inserted by default
3. Import from Airtable
   1. Airtable record ID is marked as primary key for imported records, and is mapped to field ncRecordId [datatype: varchar]
   2. If a new record is inserted after migration & if ncRecordId field was omitted during record insertion - auto generated string will be inserted by NocoDB
   3. Computed hash value for the entire record is stored in system field ncRecordHash
   4. Additional system fields created-at, updated-at are not inserted by default
4. Create new table using SDK / API
   1. No default primary key field is introduced by NocoDB. It has to be explicitly specified during table creation (using attribute pk: true)

What if Primary Key was missing?

It is possible to have a table without any primary key.

• External database table can be created without primary key configuration.
• New table can be created using SDK / API without primary key In such scenario's, new records can be created in NocoDB for this table, but records can't be updated or deleted [as there is now way for NocoDB to uniquely identify these records]

Example : Primary Key & optional system fields during new table creation

Example : Show System Fields

Can I change the Primary Key to another column within tables ?

• You can't update Primary Key from NocoDB UI. You can reconfigure it at database level directly & trigger meta sync explicitly.