MakeUpdater() [1/2]

template<EntityValueType ENTITY>

template<ConflictAction CONFLICT_ACTION = ConflictAction::Abort>

constexpr auto sqt::DataContext< ENTITY >::MakeUpdater ( )

staticconstexprnoexcept

Creates an updater for updating all columns in the database table.

Template Parameters

CONFLICT_ACTION

The conflict action to be used when an unique constraint violation occurs. The default action is sqt::ConflictAction::Abort.

Returns

The new updater instance.

The returned updater corresponds to an UPDATE SQL statement without any conditions, so it will update all rows in the database table. To control which rows to update, use the Where() method of the updater to create a new updater with conditions.

A placeholder for the entity is implicitly added to the returned updater. To execute the updater, an entity instance must be bound.

The following code demonstrates how to use the updater:

// The entity type, assuming its table type has been defined and registered, and its
// columns' names are defined as the same as the entity's field names.
struct MyEntity {
    int id{};
    std::string name;
};
 
// Create an updater with condition.
constexpr auto updater = sqt::DataContext<MyEntity>::MakeUpdater().Where(
    sqt::Table<MyEntity>.id == 1
);
 
// Create a data context, assuming the shared_db is an opened database instance.
sqt::DataContext<MyEntity> data_context{ shared_db };
 
// Prepare the updater to create a corresponding executor.
auto executor = data_context.Prepare(updater);
 
// Bind an entity to the executor.
MyEntity entity{ 1, "The First" };
executor.BeginBindings().Bind(entity);
 
// Execute the statement.
executor.Execute();

The returned instance updates all columns of the entity type. The following alternatives provides more control over the updated columns:

• MakeNoPrimaryKeyUpdater() for updating non-primary key columns. It is typically used when updating the entity by its primary key value, reducing the unnecessary overhead of updating the primary key columns.
• MakeUpdater(ASSIGNMENTS&&...) for updating specific columns.

See also

sqt::DataContext<>::MakeNoPrimaryKeyUpdater()

sqt::DataContext<>::MakeUpdater(ASSIGNMENTS&&... assignments)