我试图从表中选择3个随机记录,前提是结果应包含至少一个值“number”大于3的记录。
示例表:
+--------+-------+--------+
| ID | name | number |
+--------+-------+--------+
| 1 | name1 | 5 |
+--------+-------+--------+
| 2 | name2 | 0 |
+--------+-------+--------+
| 3 | name3 | 2 |
+--------+-------+--------+
| 4 | name4 | 7 |
+--------+-------+--------+
| 5 | name5 | 9 |
+--------+-------+--------+
| 6 | name6 | 1 |
+--------+-------+--------+
| etc... | | |
+--------+-------+--------+
因此结果可能是具有ID的记录:1,2和6.或1,4和9.但不是2,3和6,因为该结果不包括至少一个记录,其中'number'> 3。
我尝试了这个,但它无法返回总是包含至少一个值大于3的记录的结果:
SELECT name, number FROM table
WHERE EXISTS (
SELECT number FROM table
WHERE number > 3
)
ORDER BY RAND()
LIMIT 3
我想我走错了路......任何帮助都将不胜感激!
使用CTE创建所有可能的组合,以通过使用交叉连接进行选择:
WITH cte AS (
SELECT
n1.id id1, n1.name name1, n1.number number1,
n2.id id2, n2.name name2, n2.number number2,
n3.id id3, n3.name name3, n3.number number3
FROM numbers n1 CROSS JOIN numbers n2 CROSS JOIN numbers n3
WHERE
(n1.number > 3 OR n2.number > 3 OR n3.number > 3)
AND n1.id <> n2.id AND n1.id <> n3.id AND n3.id <> n2.id
ORDER BY RAND() LIMIT 1
)
SELECT id1 id, name1 name, number1 number FROM cte
UNION ALL
SELECT id2 id, name2 name, number2 number FROM cte
UNION ALL
SELECT id3 id, name3 name, number3 number FROM cte
见demo