Mysql 如果表为空或满足联接条件，则插入
对于核心sqler来说，这是一个很好的难题 表2：拍卖和投标Mysql 如果表为空或满足联接条件，则插入,mysql,sql,Mysql,Sql,对于核心sqler来说，这是一个很好的难题 表2：拍卖和投标 CREATE TABLE auctions ( id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT, created_at INT, timer INT DEFAULT 10, user_id BIGINT UNSIGNED )ENGINE=InnoDB; CREATE TABLE bids ( id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT, cr
CREATE TABLE auctions
(
id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
created_at INT,
timer INT DEFAULT 10,
user_id BIGINT UNSIGNED
)ENGINE=InnoDB;
CREATE TABLE bids
(
id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
created_at INT,
user_id BIGINT UNSIGNED,
auction_id BIGINT UNSIGNED
)ENGINE=InnoDB;
- 上一次出价创建时间不到拍卖时间秒
- 此次拍卖没有出价
INSERT INTO bids (user_id, auction_id)
SELECT 1, a.id
FROM auctions AS a, bids AS b
WHERE a.id = b.auction_id
AND a.user_id IS NULL
AND a.id = 1
AND (UNIX_TIMESTAMP() - b.created_at) < a.timer
LIMIT 1
插入投标（用户id、拍卖id）
选择1，a.id
从作为a的拍卖，到作为b的出价
其中a.id=b.id
并且a.user\u id为空
a.id=1
和（UNIX_TIMESTAMP（）-b.created_at）它可以工作，但我不知道如何将“给定拍卖id是否存在出价”逻辑放在里面。您可以使用子查询来确定是否有出价被放入拍卖。也许是这样的：
OR NOT EXISTS (SELECT * FROM bids WHERE auction_id = ?)
如果我理解正确，您需要一个外部连接（可选）的出价。像这样：
INSERT INTO bids (user_id, auction_id)
SELECT 1, a.id
FROM auctions AS a
left outer join bids AS b
ON a.id = b.auction_id
AND (UNIX_TIMESTAMP() - b.created_at) < a.timer
where
(a.user_id IS NULL
AND a.id = 1
) OR
b.id IS NULL --this will be true if there is no bid present
LIMIT 1
插入投标（用户id、拍卖id）
选择1，a.id
从拍卖到拍卖
左外连接为b
在a.id=b.id上
和（UNIX_TIMESTAMP（）-b.created_at）