MySQL:如果这是真的，如果不是，那么这是

Question

我的查询:

SELECT *
FROM ranks
WHERE
    (price = 25.00 AND accumulate = 0)
    OR
    (price <= (SELECT SUM(amount) FROM donations WHERE username = 'username' AND amount IN (SELECT price FROM ranks WHERE accumulate = 1)))
ORDER BY price
DESC LIMIT 1

基本上，如果找到匹配项，我想返回第一个 where 子句，否则返回第二个子句。

Answer 1

此查询将起作用

SELECT *
FROM ranks
WHERE price = 25.00 AND accumulate = 0

UNION ALL

SELECT *
FROM ranks
WHERE NOT EXISTS(SELECT *
                  FROM ranks
                  WHERE price = 25.00 AND accumulate = 0)
      AND (price <= (SELECT SUM(amount) FROM donations WHERE username = 'username' AND        amount IN (SELECT price FROM ranks WHERE accumulate = 1)))
ORDER BY price
DESC LIMIT 1