返回SQL SELECT查询等于行数

Question

SELECT * FROM TABLE_NAME 
WHERE category=1 AND NUMBER=4 OR NUMBER=10 
ORDER BY RANDOM() LIMIT 10

Answer 1

使用UNION ALL的正确语法：

(SELECT t.*
 FROM TABLE_NAME t
 WHERE category = 1 AND NUMBER = 4
 ORDER BY RAND()
 LIMIT 10
) UNION ALL
(SELECT t.*
 FROM TABLE_NAME t
 WHERE category = 1 AND NUMBER = 10
 ORDER BY RAND()
 LIMIT 10
);

这假设每个组都有足够数量的记录。

rand()可能不是您想要完成的任务所必需的。如果您有大量的数据，那么它确实会增加很多开销。