sqlgen/docs/drop.md

sqlgen::drop

The sqlgen::drop interface provides a type-safe way to drop tables from a SQL database. It supports the if_exists clause to handle cases where the table may not exist.

Usage

Basic Drop

Drop a table:

const auto conn = sqlgen::sqlite::connect("database.db");

sqlgen::drop<Person>(conn).value();

This generates the following SQL:

DROP TABLE "Person";

Note that conn is actually a connection wrapped into an sqlgen::Result<...>. This means you can use monadic error handling and fit this into a single line:

// sqlgen::Result<Ref<Connection>>
const auto result = sqlgen::sqlite::connect("database.db").and_then(
                        sqlgen::drop<Person>);

Please refer to the documentation on sqlgen::Result<...> for more information on error handling.

With if_exists clause

Drop a table only if it exists:

using namespace sqlgen;

const auto query = drop<Person> | if_exists;

query(conn).value();

This generates the following SQL:

DROP TABLE IF EXISTS "Person";

You can also use monadic error handling here:

using namespace sqlgen;

const auto query = drop<Person> | if_exists;

// sqlgen::Result<Ref<Connection>>
const auto result = sqlite::connect("database.db").and_then(query);

Example: Full Query Composition

using namespace sqlgen;

const auto query = drop<Person> | if_exists;

const auto result = query(conn);

if (!result) {
    // Error handling
}

This generates the following SQL:

DROP TABLE IF EXISTS "Person";

It is strongly recommended that you use using namespace sqlgen. However, if you do not want to do that, you can rewrite the example above as follows:

const auto query = sqlgen::drop<Person> | sqlgen::if_exists;

const auto result = query(conn);

Notes

• The if_exists clause is optional - if omitted, the query will fail if the table doesn't exist
• The Result<Ref<Connection>> type provides error handling; use .value() to extract the result (will throw an exception if there's an error) or handle errors as needed or refer to the documentation on sqlgen::Result<...> for other forms of error handling.
• The table name is derived from the struct name (e.g., Person becomes "Person" in SQL)