mysql實現隨機獲取幾條資料的方法
sql語句有幾種寫法
1：SELECT * FROM tablename ORDER BY RAND() LIMIT 想要獲取的資料條數；
2：SELECT *FROM `table` WHERE id >= (SELECT FLOOR( MAX(id) * RAND()) FROM `table` ) ORDER BY id LIMIT 想要獲取的資料條數;
3：SELECT
* FROM
`table` AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM
`table`)) AS id) AS t2 WHERE t1.id >=
t2.id
ORDER BY t1.id ASC LIMIT 想要獲取的資料條數;
4：SELECT * FROM `table`WHERE id >= (SELECT floor(RAND() * (SELECT MAX(id) FROM `table`))) ORDER BY id LIMIT 想要獲取的資料條數;
5：SELECT
* FROM
`table` WHERE id >= (SELECT floor( RAND() * ((SELECT MAX(id) FROM
`table`)-(SELECT MIN(id) FROM
`table`)) + (SELECT MIN(id) FROM
`table`
6：SELECT * FROM `table` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `table`)-(SELECT MIN(id) FROM `table`))+(SELECT MIN(id) FROM `table`)) AS id) AS t2 WHERE t1.id >= t2.id ORDER BY t1.id LIMIT 想要獲取的資料條數;
1的查詢時間>>2的查詢時間>>5的查詢時間>6的查詢時間>4的查詢時間>3的查詢時間，也就是3的效率最高。