# Type User-defined types are special types that can associate multiple named fields to a single column. [SchemaBuilder](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/querybuilder/SchemaBuilder.html) offers API methods for creating, altering, and dropping types. ## Creating a Type (CREATE TYPE) To start a `CREATE TYPE` query, use `createType` in [SchemaBuilder](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/querybuilder/SchemaBuilder.html): ```java import static com.datastax.oss.driver.api.querybuilder.SchemaBuilder.*; CreateTypeStart create = createType("mykeyspace", "address"); ``` Like all other `CREATE` queries, one may supply `ifNotExists()` to require that the type should only be created if it doesn’t already exist, i.e.: ```java CreateTypeStart create = createType("address").ifNotExists(); ``` Note that, at this stage, the query cannot be completed yet. You need to provide at least one field using `withField()`, i.e.: ```java CreateType create = createType("mykeyspace", "address").withField("street", DataTypes.TEXT); // CREATE TYPE mykeyspace.address (street text) ``` A type with only one field is not entirely useful. You may continue to make successive calls to `withField` to specify additional fields, i.e.: ```java CreateType create = createType("mykeyspace", "address") .withField("street", DataTypes.TEXT) .withField("city", DataTypes.TEXT) .withField("zip_code", DataTypes.INT) .withField("phones", DataTypes.setOf(DataTypes.TEXT)); // CREATE TYPE mykeyspace.address (street text,city text,zip_code int,phones set) ``` ## Using a created Type in Schema Builder API After creating a UDT, one may wonder how to use it in other schema statements. To do so, utilize `udt(name,frozen)` from [SchemaBuilder](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/querybuilder/SchemaBuilder.html), i.e: ```java CreateTable users = createTable("mykeyspace", "users") .withPartitionKey("id", DataTypes.UUID) .withColumn("name", udt("fullname", true)) .withColumn("name", DataTypes.setOf(udt("direct_reports", true))) .withColumn("addresses", DataTypes.mapOf(DataTypes.TEXT, udt("address", true))); // CREATE TABLE mykeyspace.users (id uuid PRIMARY KEY,name set>,addresses map>) ``` ## Altering a Type (ALTER TYPE) To start an `ALTER TYPE` query, use `alterType`: ```java alterTable("mykeyspace", "address"); ``` From here, you can modify the type in the following ways: * `addField(fieldName, dataType)`: Adds a new field to the type. * `alterField(fieldName, dataType)`: Changes the type of an existing field. This is not recommended. * `renameField(from, to)`: Renames a field. Invoking any of these methods returns a complete query. You may make successive calls to `renameField`, but not the other methods. ## Dropping a Type (DROP TYPE) To create a `DROP TYPE` query, use `dropType`: ```java dropType("mykeyspace", "address"); // DROP TYPE mykeyspace.address ``` You may also specify `ifExists`: ```java dropTable("address").ifExists(); // DROP TYPE IF EXISTS address ```