Question

我正在尝试创建一个mysql查询来选择让我们说前5行和5行，具体取决于当前ID。这是我想要使用的查询：

SELECT * FROM posts WHERE PID<='10' ORDER BY PID DESC LIMIT 7
UNION ALL
SELECT * FROM posts WHERE PID>'10' ORDER BY PID ASC LIMIT 6

但出于某种原因，查询无效。我错过了什么吗？我在论坛帖子中找到了这个解决方案。

Answer 1

PID可能是 int 类型。所以你应该使用以下（ SQL Fiddle ）：

(SELECT * FROM posts WHERE PID <= 10 ORDER BY PID DESC LIMIT 7)
UNION ALL
(SELECT * FROM posts WHERE PID > 10 ORDER BY PID ASC LIMIT 6)

正如您所看到的，两个查询的顺序也是单独维护的。

Answer 2

试试这个：

(SELECT *
 FROM posts
 WHERE PID <= '10'
 ORDER BY PID DESC LIMIT 7
 )
UNION ALL
(SELECT *
 FROM posts
 WHERE PID > '10'
 ORDER BY PID ASC LIMIT 6
 )
ORDER BY PID ASC;

sqlfiddle demo

Answer 3

DOCS

要将ORDER BY或LIMIT应用于单个SELECT，请将该子句放在括起SELECT的括号内：

mysql选择n行之前和n行之后

3 个答案: