Mysql 使用上一行的值更新列

Question

我在 MySQL 中有一个表，例如:

SELECT time_stamp, price,prev_price, FROM prices ORDER by time_stamp ASC;

-------------------------------
time_stamp | price | prev_price
-------------------------------
1382457241 |  23.3 | NULL
1393553097 |  14.2 | NULL
1412857868 |  16.0 | NULL
1412857965 | 201.1 | NULL
........

我想要一个 UPDATE 语句用前一行的价格值更新 prev_price(按时间戳排序):

-------------------------------
time_stamp | price | prev_price
-------------------------------
1382457241 |  23.3 | NULL
1393553097 |  14.2 | 23.3
1412857868 |  16.0 | 14.2
1412857965 | 201.1 | 16.0
........

MySQL 版本:5.7.24:

mysql> select version();
+-------------------------+
| version()               |
+-------------------------+
| 5.7.24-0ubuntu0.16.04.1 |
+-------------------------+

Answer 1

试试这个:

SELECT time_stamp,
       price,
       (SELECT e2.price
        FROM example e2
        WHERE e2.time_stamp < e1.time_stamp
        ORDER BY e2.time_stamp DESC
        LIMIT 1
       ) AS prev_price
FROM example e1
ORDER BY e1.time_stamp ASC