belongs_to_many

Many-to-many through a pivot table. through is required and names the pivot table:

#[repository(table = "post")]
#[belongs_to_many(table = "tag", through = "post_tag")]
pub trait PostRepository: Repository {
    // tag_name → JOIN "post_tag" ON "post_tag".post_id = "post".id
    //            JOIN "tag" ON "tag".id = "post_tag".tag_id
    //            WHERE "tag".name = $1
    async fn find_all_by_tag_name(&self, name: String) -> sqlx::Result<Vec<PostRow>>;
}

fk (default "{this_table}_id", e.g. post_id) is this table's FK column in the pivot table; other_fk (default "{table}_id", e.g. tag_id) is the target table's FK column in the pivot. Override either explicitly if the pivot's column names don't follow that convention:

#[belongs_to_many(table = "tag", through = "post_tag", fk = "post_pk", other_fk = "tag_pk")]

Only legal on find_all_by_* — same reasoning as has_many: a matching pivot row can multiply the base row, see Fan-out.

See relations for the full attribute table and defaults.