addPrimaryKey

The addPrimaryKey Change Type adds a primary key out of an existing column or set of columns.

Uses

It is a best practice to normalize the data in your relational database by setting a primary key on one or more of the columns of a table. A table can only have one primary key, regardless of whether that key is single or composite. You can use the primary key to uniquely identify each row in the table.

Running the addPrimaryKey Change Type

To run this Change Type, follow these steps:

1. Add the Change Type to your changeset, as shown in the examples on this page.
2. Specify any required attributes. Use the table on this page to see which ones your database requires.
3. Deploy your changeset by running the update command:

liquibase update

Add new column to existing primary key

If you have already set a primary key on a column, but you realize that column by itself does not provide sufficient uniqueness to each row, you can add an additional column to the existing key. Liquibase returns an error if you try to create a new primary key because one already exists. Instead, follow these steps:

1. Drop the existing primary key with the dropPrimaryKey Change Type:

   <changeSet author="liquibase-docs" id="dropPrimaryKey-example">
       <dropPrimaryKey  tableName= "existing_table" constraintName="primary_key_constraint"/>
   </changeSet>

2. Add new column to the existing table with the addColumn Change Type:

   <changeSet author="liquibase-docs" id="addColumn-example"> 
       <addColumn tableName="existing_table">
           <column name="new_column" type="VARCHAR(256)">
               <constraints nullable="false"/>
           </column>
       </addColumn>
   </changeSet>

3. Add a composite primary key to the table, including both the new and old columns:

   <changeSet author="liquibase-docs" id="addPrimaryKey-example">
       <addPrimaryKey tableName="existing_table" columnNames="existing_column,new_column" constraintName="primary_key_constraint"/>
   </changeSet>

4. Deploy your changes:

   liquibase update

Available attributes

Examples

--liquibase formatted sql

--changeset liquibase-docs:addPrimaryKey-example
ALTER  TABLE  cat.person  ADD  PRIMARY  KEY  (id, name);

databaseChangeLog:
-  changeSet:
    id:  addPrimaryKey-example
    author:  liquibase-docs
    changes:
    -  addPrimaryKey:
        catalogName:  cat
        clustered:  true
        columnNames:  id, name
        constraintName:  pk_person
        forIndexName:  A String
        schemaName:  public
        tableName:  person
        tablespace:  A String
        validate:  true

{
    "databaseChangeLog": [
        {
            "changeSet": {
                "id": "addPrimaryKey-example",
                "author": "liquibase-docs",
                "changes": [
                    {
                        "addPrimaryKey": {
                            "catalogName": "cat",
                            "clustered": true,
                            "columnNames": "id, name",
                            "constraintName": "pk_person",
                            "forIndexName": "A String",
                            "schemaName": "public",
                            "tableName": "person",
                            "tablespace": "A String",
                            "validate": true
                        }
                    }
                ]
            }
        }
    ]
}

<databaseChangeLog
    xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:ext="http://www.liquibase.org/xml/ns/dbchangelog-ext"
    xmlns:pro="http://www.liquibase.org/xml/ns/pro"
    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd
        http://www.liquibase.org/xml/ns/dbchangelog-ext
        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-ext.xsd
        http://www.liquibase.org/xml/ns/pro
        http://www.liquibase.org/xml/ns/pro/liquibase-pro-latest.xsd">

    <changeSet  author="liquibase-docs"  id="addPrimaryKey-example">
        <addPrimaryKey  catalogName="cat"
            clustered="true"
            columnNames="id, name"
            constraintName="pk_person"
            forIndexName="A String"
            schemaName="public"
            tableName="person"
            tablespace="A String"
            validate="true"/>
    </changeSet>

</databaseChangeLog>

Database support