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 add a primary key to your table, follow these steps:

Add the addPrimaryKey Change Type to your changeset with the needed attributes, as shown in the examples.
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:

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>

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>

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>

Deploy your changes:
```
liquibase update
```

Available attributes

Name	Description	Required for	Supports
`catalogName`	Name of the catalog		all
`clustered`	Boolean. Whether to create a clustered index		all
`columnNames`	Name of the column(s) to create the primary key on. Comma separated if multiple	all	all
`constraintName`	Name of the constraint for the primary key		all
`forIndexCatalogName`	Name of the catalog of the index to associate with the primary key		all
`forIndexName`	Name of the index to associate with the primary key		db2, db2z, oracle
`forIndexSchemaName`	Name of the schema of the index to associate with the primary key		all
`schemaName`	Name of the schema		all
`tableName`	Name of the table to create the primary key on	all	all
`tablespace`	Name of the tablespace to use for the primary key		all
`validate`	Set to `true` if the constraint has `ENABLE VALIDATE` set, or `false` if the constraint has `ENABLE NOVALIDATE` set.		all

XML example

...
<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>
...

YAML example

...
-  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
...

JSON example

...
{
  "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
            }
        }]
    }
}
...

SQL example

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

Database support