APriori MySQL

SELECT
    x.id_barang AS barang1,
    y.id_barang AS barang2,
    COUNT(*) AS frekuensi,
    ROUND(COUNT(x.id_barang AND y.id_barang)/(SELECT COUNT(*) FROM tbl_detail_transaksi GROUP BY id_transaksi)*100,1) AS support
FROM
    tbl_detail_transaksi x,
    tbl_detail_transaksi y
WHERE
    x.id_barang<y.id_barang
    AND x.id_transaksi=y.id_transaksi
GROUP BY
    x.id_barang, y.id_barang