From 1980 to 2000, which artist had the most disco releases?
From 1980 to 2000 refers to groupYear between 1980 and 2000; tag = 'disco'; the most releases refer to MAX(COUNT(id));
SELECT T1.artist FROM torrents AS T1 INNER JOIN tags AS T2 ON T1.id = T2.id WHERE T1.groupYear BETWEEN 1980 AND 2000 AND T2.tag LIKE 'disco' GROUP BY T1.artist ORDER BY COUNT(T2.tag) DESC LIMIT 1
CREATE TABLE IF NOT EXISTS "torrents"
(
    groupName     TEXT,
    totalSnatched INTEGER,
    artist        TEXT,
    groupYear     INTEGER,
    releaseType   TEXT,
    groupId       INTEGER,
    id            INTEGER
        constraint torrents_pk
            primary key
);
CREATE TABLE IF NOT EXISTS "tags"
(
    "index" INTEGER
        constraint tags_pk
            primary key,
    id      INTEGER
        constraint tags_torrents_id_fk
            references torrents,
    tag     TEXT
);
CREATE INDEX ix_tags_index
    on tags ("index");
