MySQL LIMIT使用SELECT COUNT（*）作为SELECT中的值

Question

尝试做这样的事情：

{{1}}

虽然不适合我。

Answer 1

我认为你正在尝试做这样的事情：

MYKEY

您不能将子查询用于SELECT e.* FROM events e WHERE e.start_time >= DATE_SUB(NOW(), INTERVAL 6 HOUR) AND e.start_time < NOW() UNION ALL (SELECT e.* FROM events e WHERE e.start_time >= NOW() ORDER BY e.start_time LIMIT 100 ) ORDER BY start_time; 参数。

Answer 2

不可能像查询一样使用查询作为LIMIT函数的变量。我建议这样的查询：

SELECT *
FROM events
WHERE (
  start_time >= DATE_SUB(NOW(),INTERVAL 6 HOUR) AND
  start_time < NOW()
)
UNION ALL (
  SELECT *
  FROM events
  WHERE start_time >= NOW()
  ORDER BY start_time
  LIMIT 100
)
ORDER BY start_time ASC;

Here是一个有效的方法。

Answer 3

您可以设置限制变量并使用它。

SET @limit= (
    SELECT COUNT(*) FROM events WHERE
        start_time >= DATE_SUB(NOW(),INTERVAL 6 HOUR)
    AND
        start_time < NOW()
   )+100;

SELECT * FROM events WHERE
    start_time >= DATE_SUB(NOW(),INTERVAL 6 HOUR)
LIMIT @limit
ORDER BY start_time ASC;