将查询转换为计数行

Question

如何转换此查询以获取行数？

SELECT IF(rz_price_grn != 0, rz_price_grn, ROUND(rz_price2 * currencies.`rate`)) AS `ssc_price`, rz_price_grn, rz_price2, IF(price IS NULL, 0, price) AS `goods_price`
FROM rz_price
LEFT JOIN currencies ON currencies.`name` = 'USD'
LEFT JOIN  goods ON goods.id = rz_price.`rz_art`
LEFT JOIN rz_archive ON rz_archive.rz_art  = rz_price.rz_art
WHERE
 rz_archive.rz_art IS NULL
HAVING ROUND(ssc_price, 2) != ROUND(goods_price, 2)
LIMIT 500000

Answer 1

这可行吗？

SELECT Count(*)
FROM rz_price
LEFT JOIN currencies ON currencies.`name` = 'USD'
LEFT JOIN  goods ON goods.id = rz_price.`rz_art`
LEFT JOIN rz_archive ON rz_archive.rz_art  = rz_price.rz_art
WHERE
 rz_archive.rz_art IS NULL
 AND (ROUND(IF(rz_price_grn != 0, rz_price_grn, ROUND(rz_price2 * currencies.`rate`)), 2) != ROUND(IF(price IS NULL, 0, price), 2))
--LIMIT 500000

Answer 2

那么，

SELECT COUNT(
    SELECT IF(rz_price_grn != 0, rz_price_grn, ROUND(rz_price2 * currencies.`rate`)) AS `ssc_price`, rz_price_grn, rz_price2, IF(price IS NULL, 0, price) AS `goods_price`
    FROM rz_price
    LEFT JOIN currencies ON currencies.`name` = 'USD'
    LEFT JOIN  goods ON goods.id = rz_price.`rz_art`
    LEFT JOIN rz_archive ON rz_archive.rz_art  = rz_price.rz_art
    WHERE
     rz_archive.rz_art IS NULL
    HAVING ROUND(ssc_price, 2) != ROUND(goods_price, 2)
)

有效吗？