CREATE TABLE sys_admin.layer_groups (
    name varchar PRIMARY KEY
);

CREATE TABLE sys_admin.grouped_layers (
    group_name varchar REFERENCES sys_admin.layer_groups ON DELETE CASCADE,
    schema     varchar,
    name       varchar,
    ord        int NOT NULL DEFAULT 0,
    PRIMARY KEY (group_name, schema, name),
    UNIQUE (group_name, schema, name, ord),
    FOREIGN KEY(schema, name) REFERENCES sys_admin.published_services
);