SQL database support - MichaelMiller-/sec21 GitHub Wiki
With the help of the reflection library, it is very easy to map data structures as SQL tables.
struct user
{
std::string name{};
std::string password{};
int karma{};
double cash{};
};
template <>
struct sec21::reflection::table<user>
{
static constexpr auto name = "user";
struct columns
{
using name = column<"name", &user::name, database::primary_key, database::not_null>;
using password = column<"password", &user::password, database::not_null>;
using karma = column<"karma", &user::karma>;
using cash = column<"cash", &user::cash>;
};
using metainfo = std::tuple<
columns::name,
columns::password,
columns::karma,
columns::cash>;
};As you can see the original data structure is not changed. Instead, the table is specified by the template specialization of the reflection::table class. In addition, the first two columns are given freely selectable keywords as constraints. This is followed by a data type mapping for the corresponding database dialect. In this case, PostgreSQL data types are mapped.
namespace sec21::database
{
template <>
struct column_type<int>
{
static constexpr std::string_view value = "INT";
};
template <>
struct column_type<std::string>
{
static constexpr std::string_view value = "TEXT";
};
template <>
struct column_type<double>
{
static constexpr std::string_view value = "REAL";
};
} // namespace sec21::databaseIn the database library there are various functions to generate SQL statements.
{
auto sql_statement = sec21::database::create_table<user>();
// sql_statement = "CREATE TABLE user(name TEXT PRIMARY KEY NOT NULL,password TEXT NOT NULL,karma INT,cash REAL);"
}
{
user obj{.name = "John Doe", .password = "hidden", .karma = 42, .cash = 3.14};
auto sql_statement = sec21::database::insert_into(obj);
// sql_statement == "INSERT INTO user (name,password,karma,cash) VALUES ('John Doe','hidden',42,3.14);"
}