将 bigint unsigned 列转换为 bigint signed 失败答案

【问题标题】：Conversion of bigint unsigned column to bigint signed fails将 bigint unsigned 列转换为 bigint signed 失败
【发布时间】：2021-06-23 12:27:12
【问题描述】：

MySql 数据库版本 7.0 中出现语法错误

SELECT
    r.id,
    r.number,
    r.numbertype,
    r.forhandler,
    LAG(r.number) OVER (PARTITION BY r.numbertype ORDER BY r.number) AS last_row_number,
    LEAD(r.number) OVER (PARTITION BY r.numbertype ORDER BY r.number) AS next_row_number,
    r.number -(LAG(r.number) OVER (PARTITION BY r.numbertype ORDER BY r.number)) AS gap_last_rk,
    CAST (r.number-(LEAD(r.number) OVER (PARTITION BY r.numbertype ORDER BY r.`number`)) AS BIGINT SIGNED)  AS gap_next_rk

FROM admin.numberranges r
WHERE r.status=2
ORDER BY r.number;

语法错误出现在我的 CAST 部分。我的 NUMBER 列是 BIG INT UNSIGNED。

我也尝试过转换 -:(

Error Code: 1064
You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'BIGINT SIGNED) AS neg_number

【问题讨论】：

标签有助于吸引可以帮助回答问题的人的注意力。从错误消息中可以清楚地看出，OP 使用的是 MariaDB，而不是 MySQL。这些是不同的软件产品。 MariaDB 于 2010 年开始作为 MySQL 的一个分支，但现在它有很多不同之处，以至于它应该被视为一个不同的、不兼容的产品。

标签： mariasql

【解决方案1】：

首先，CAST 后面有一个空格，这可能会导致您的问题出现其他解析错误/问题。您必须使用CAST(...)。其次，BIGINT SIGNED 类型是不允许的，请查看CAST(expr AS type) 的列表。当您需要签名号码时，请使用 SIGNED 或 SIGNED INTEGER 类型，如文档中所述：

类型可以是以下值之一：

[...]

签名 [整数]

有关如何使用CAST() 函数的示例请参阅以下查询（示例在 MySQL 8.0.23 上运行，MariaDB 的结果可能不一样但类型限制相似，请参阅MySQL documentation of CONVERT(expr, type)）：

mysql> EXPLAIN Dummy;
+-------+-----------------+------+-----+---------+-------+
| Field | Type            | Null | Key | Default | Extra |
+-------+-----------------+------+-----+---------+-------+
| Test  | bigint unsigned | YES  |     | NULL    |       |
+-------+-----------------+------+-----+---------+-------+
1 row in set (0.01 sec)

mysql> SELECT Test, CAST(Test AS BIGINT SIGNED) FROM Dummy;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
                    corresponds to your MySQL server version for the right syntax
                    to use near 'BIGINT SIGNED) FROM Dummy' at line 1
mysql> SELECT Test, CAST(Test AS SIGNED) FROM Dummy;
+------+----------------------+
| Test | CAST(Test AS SIGNED) |
+------+----------------------+
| 1234 |                 1234 |
+------+----------------------+
1 row in set (0.00 sec)

【讨论】：