Question

如何删除所有超过一天但从第五行开始的行（如果存在！）？

MYSQL数据库的布局：

user |post|timestamp
Harry foo  1445275458

（时间戳是CURRENT_TIMESTAMP）

Answer 1

鉴于此示例数据被Drew无耻地窃取并延长：

select t1.*, from_unixtime(tstamp) from t1;

| id | fname | lname |     tstamp |     from_unixtime(tstamp) |
|----|-------|-------|------------|---------------------------|
|  1 | Harry |   foo | 1445275458 | October, 19 2015 17:24:18 |
|  2 | Harry |   foo | 1445275457 | October, 19 2015 17:24:17 |
|  3 | Harry |   foo | 1445275456 | October, 19 2015 17:24:16 |
|  4 | Harry |   foo | 1445275455 | October, 19 2015 17:24:15 |
|  5 | Harry |   foo | 1445275454 | October, 19 2015 17:24:14 |
|  6 | Harry |   foo | 1445275453 | October, 19 2015 17:24:13 |
|  7 | Harry |   foo | 1445275452 | October, 19 2015 17:24:12 |
|  8 | Harry |   foo | 1345275458 |  August, 18 2012 07:37:38 |
|  9 | Harry |   foo | 1435275458 |    June, 25 2015 23:37:38 |

使用此查询

DELETE t1.* 
FROM t1
LEFT JOIN (SELECT id FROM t1 ORDER BY tstamp DESC LIMIT 5) q ON t1.id = q.id
WHERE q.id IS NULL
AND t1.tstamp < NOW() - INTERVAL 1 DAY;

您会得到以下结果：

select t1.*, from_unixtime(tstamp) from t1;

| id | fname | lname |     tstamp |     from_unixtime(tstamp) |
|----|-------|-------|------------|---------------------------|
|  1 | Harry |   foo | 1445275458 | October, 19 2015 17:24:18 |
|  2 | Harry |   foo | 1445275457 | October, 19 2015 17:24:17 |
|  3 | Harry |   foo | 1445275456 | October, 19 2015 17:24:16 |
|  4 | Harry |   foo | 1445275455 | October, 19 2015 17:24:15 |
|  5 | Harry |   foo | 1445275454 | October, 19 2015 17:24:14 |

看到它在sqlfiddle

从第五行开始删除超过一天的行

1 个答案: