Select()

template<EntityValueType ENTITY>

template<typename E = ENTITY>
requires PrimaryKeyEntityValueType<E>

std::optional< E > sqt::DataContext< ENTITY >::Select

(

const typename TableType< E >::PrimaryKeyType::ValueType &

primary_key

)

Retrieves a single entity by the specified primary key value from the database table.

Parameters

primary_key

The primary key value of the entity to be retrieved.

Returns

The entity if found; otherwise, std::nullopt if the entity with the specified primary key value does not exist.

Exceptions

sqt::SQLError

Thrown if the selection fails.

Note

This method is only available if the entity type has a primary key. Use the SQT_PRIMARY_KEY or SQT_PRIMARY_KEY_AUTO_INC macro to define a primary key.

For more control over which entities to retrieve, use the MakeSelecter() method from the complex style interface to create a selecter and apply custom conditions. Furthermore, use the MakeSelecter(const COLUMNS&...) method to specify which columns of the entity to select.

See also

sqt::DataContext<>::MakeSelecter()

sqt::DataContext<>::MakeSelecter(const COLUMNS&... columns)

sqt::DataContext<>::SelectAll()

SQT_PRIMARY_KEY

SQT_PRIMARY_KEY_AUTO_INC