# Update methods Annotate a DAO method with [@Update](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/mapper/annotations/Update.html) to generate a query that updates one or more [entities](): ```java @Dao public interface ProductDao { @Update void update(Product product); } ``` ## Parameters The first parameter must be an entity instance. All of its non-PK properties will be interpreted as values to update. * If the annotation doesn’t have a `customWhereClause`, the mapper defaults to an update by primary key (partition key + clustering columns). The WHERE clause is generated automatically, and bound with the PK components of the provided entity instance. The query will update at most one row. * If the annotation has a `customWhereClause`, it completely replaces the WHERE clause. If the provided string contains placeholders, the method must have corresponding additional parameters (same name, and a compatible Java type): ```java @Update(customWhereClause = "description LIKE :searchString") void updateIfDescriptionMatches(Product product, String searchString); ``` The PK components of the provided entity are ignored. Multiple rows may be updated. If the query has a custom timestamp or TTL with placeholders, the method must have corresponding additional parameters (same name, and a compatible Java type): ```java @Update(timestamp = ":timestamp") void updateWithTimestamp(Product product, long timestamp); @Update(ttl = ":ttl") void updateWithTtl(Product product, int ttl); ``` An optional IF clause can be appended to the generated query. It can contain placeholders, for which the method must have corresponding parameters (same name, and a compatible Java type): ```java @Update(customIfClause = "description = :expectedDescription") ResultSet updateIfDescriptionMatches(Product product, String expectedDescription); ``` An optional IF EXISTS clause at the end of the generated UPDATE query. This is mutually exclusive with `customIfClause` (if both are set, the mapper processor will generate a compile-time error): ```java @Update(ifExists = true) boolean updateIfExists(Product product); ``` The annotation can define a [null saving strategy]() that applies to the properties of the entity to update. This allows you to implement partial updates, by passing a “template” entity that only contains the properties you want to modify: ```java // DAO method definition: @Update(customWhereClause = "id IN (:id1, :id2)", nullSavingStrategy = DO_NOT_SET) void updateWhereIdIn(Product product, UUID id1, UUID id2); // Client code: Product template = new Product(); template.setDescription("Coming soon"); // all other properties remain null dao.updateWhereIdIn(template, 42, 43); // Will only update 'description' on the selected rows ``` A `Function` or `UnaryOperator` can be added as the **last** parameter. It will be applied to the statement before execution. This allows you to customize certain aspects of the request (page size, timeout, etc) at runtime. See [statement attributes](). ## Return type The method can return: * `void`. * a `boolean` or [Boolean](https://docs.oracle.com/javase/8/docs/api/index.html?java/lang/Boolean.html), which will be mapped to `ResultSet#wasApplied()`. This is intended for conditional queries. ```java @Update(ifExists = true) boolean updateIfExists(Product product); ``` * a [ResultSet](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/core/cql/ResultSet.html). The method will return the raw query result, without any conversion. This is intended for queries with custom IF clauses; when those queries are not applied, they return the actual values of the tested columns. ```java @Update(customIfClause = "description = :expectedDescription") ResultSet updateIfExists(Product product); // if the condition fails, the result set will contain columns '[applied]' and 'description' ``` * a [BoundStatement](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/core/cql/BoundStatement.html). This is intended for queries where you will execute this statement later or in a batch: ```java @Update BoundStatement update(Product product); ``` * a [CompletionStage](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletionStage.html) or [CompletableFuture](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html) of any of the above. The mapper will execute the query asynchronously. Note that for result sets, you need to switch to the asynchronous equivalent [AsyncResultSet](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/core/cql/AsyncResultSet.html). ```java @Update CompletionStage update(Product product); @Update(ifExists = true) CompletableFuture updateIfExists(Product product); @Update(customIfClause = "description = :expectedDescription") CompletableFuture updateIfDescriptionMatches(Product product, String expectedDescription); ``` * a [ReactiveResultSet](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/dse/driver/api/core/cql/reactive/ReactiveResultSet.html). ```java @Update ReactiveResultSet updateReactive(Product product); ``` * a [custom type](). ## Target keyspace and table If a keyspace was specified [when creating the DAO](), then the generated query targets that keyspace. Otherwise, it doesn’t specify a keyspace, and will only work if the mapper was built from a session that has a [default keyspace](https://java-driver.docs.scylladb.com/scylla-4.19.0.x/api/com/datastax/oss/driver/api/core/session/SessionBuilder.html#withKeyspace-com.datastax.oss.driver.api.core.CqlIdentifier-) set. If a table was specified when creating the DAO, then the generated query targets that table. Otherwise, it uses the default table name for the entity (which is determined by the name of the entity class and the naming convention).