mysql排行榜sql的实现

SELECT num_rows
FROM (SELECT @rownum := @rownum + 1 AS num_rows, openid
    FROM (SELECT @rownum := 0, openid, money
        FROM lt_cash_user
        ) t
    ORDER BY money DESC
    ) t1
WHERE openid = 'oS77FjsN6hc-fWL1toDKyUM_uGTs'