SELECT
    COMBI.ITEM_A
    ,COMBI.ITEM_B
    ,ROUND(CAST(COMBI.PURCHASE_COUNT AS REAL) / (SELECT COUNT(DISTINCT MEMBER_CODE) FROM PURCHASE_HISTORY), 5) * 100 AS SUPPORT
    ,ROUND(CAST(COMBI.PURCHASE_COUNT AS REAL) / ITEM.PURCHASE_COUNT, 5) * 100 AS CONFIDENCE
    ,ROUND(CAST(COMBI.PURCHASE_COUNT AS REAL) / ITEM.PURCHASE_COUNT / ALL_B.PURCHASE_COUNT, 5) * 100 AS LIFT

FROM
    (
    SELECT
        ITEM_CODE
        ,COUNT(DISTINCT MEMBER_CODE) AS PURCHASE_COUNT
    FROM
        PURCHASE_HISTORY
    GROUP BY
        ITEM_CODE
    ) AS ITEM
INNER JOIN
    (
    SELECT
        A.ITEM_CODE AS ITEM_A
        ,B.ITEM_CODE AS ITEM_B
        ,COUNT(DISTINCT A.MEMBER_CODE) AS PURCHASE_COUNT
    FROM
        PURCHASE_HISTORY AS A
    INNER JOIN
        PURCHASE_HISTORY AS B
    ON
        A.MEMBER_CODE = B.MEMBER_CODE
    AND
        A.ITEM_CODE <> B.ITEM_CODE
    GROUP BY
        A.ITEM_CODE
        ,B.ITEM_CODE
    ) AS COMBI
ON
    COMBI.ITEM_A = ITEM.ITEM_CODE
INNER JOIN
    (
    SELECT
        ITEM_CODE
        ,CAST(COUNT(DISTINCT MEMBER_CODE) AS REAL) / (SELECT COUNT(DISTINCT MEMBER_CODE) FROM PURCHASE_HISTORY) AS PURCHASE_COUNT
    FROM
        PURCHASE_HISTORY
    GROUP BY
        ITEM_CODE
    ) AS ALL_B
ON
    COMBI.ITEM_B = ALL_B.ITEM_CODE