MySQL

MySQL:简介 Ubuntu 安装 MySQL MySQL:官方文档地址 MySQL:DDL、DQL、DML、DCL的含义 MySQL:Mac 中启动 关闭 MySQL 服务 MySQL:有哪些好用的管理工具? MySQL:命令行工具 mycli MySQL:CHAR类型 MySQL:VARCHAR类型 MySQL:整型数字 MySQL:datetime 类型 MySQL:时间戳 MySQL:创建和删除数据库 MySQL:切换和查看数据库 MySQL:创建和删除表 MySQL:在表中增加、删除、修改列 MySQL:创建和删除主键 MySQL:使用 rename 修改表名 MySQL:修改自增主键id的类型 MySQL:如何创建一个相同的表 MySQL:修改表的字符编码 MySQL:增删查改 MySQL:插入数据 MySQL:插入多行数据 MySQL:使用 insert set 插入数据 MySQL:大小写和反引号 MySQL:字符串类型值的大小写 MySQL:SQL注释 MySQL:不要使用utf8 MySQL:NULL的判等 MySQL:InnoDB存储引擎的限制 MySQL:if和case的使用 MySQL:使用 load data 快速导入数据 MySQL:使用 select into outfile 导出数据 MySQL:查询和设置 sql_mode MySQL:严格模式 MySQL:NOT NULL 字段不插入数据,会发生什么? MySQL:无符号整数列插入负数会发生什么? MySQL:关于 null 的那些事 MySQL:大表行数查询 MySQL:自动生成创建时间、更新时间;自动更新更新时间 MySQL:insert ignore MySQL:字符集排序规则 MySQL:如果连续更新一个字段两次,结果是? MySQL:字符串转数字 MySQL:尾部空格 MySQL:添加和删除索引 MySQL:唯一索引与NULL MySQL:唯一索引的单列长度限制 MySQL:InnoDB 索引 MySQL:字符集排序规则对唯一索引的影响 MySQL:唯一索引冲突消耗主键 ID MySQL 使用 index hint 指定索引:ignore index、force index、use index MySQL:查看客户端连接信息 MySQL:查看表的状态 show table status MySQL:如何治理连接数 ? MySQL:如何监控和处理慢查询与长事务 ? MySQL:自定义函数 MySQL:now() 函数 MySQL:unix_timestamp() 函数 MySQL:from_unixtime() 函数 MySQL:version() 函数 MySQL:current_timestamp() 函数 MySQL:cast 函数 MySQL:convert 函数 MySQL:使用 greatest、least 函数获取行最大值、最小值 MySQL:使用 group_concat 函数连接多行数据为一个字符串 MySQL:获取版本号 MySQL:Java 类型映射 MySQL下创建只能有一行记录的table 关于MySQL的字符集 理解数据库中的undo日志、redo日志、检查点 ubuntu下源码安装MySQL MySQL:JOIN解惑 如何快速更新数据库中的百万条数据

MySQL:字符串转数字


#MySQL


用 cast 或者 convert 函数。

整数

mysql> select cast('123' as unsigned);
+-----------------------+
| cast(123 as unsigned) |
+-----------------------+
|                   123 |
+-----------------------+
1 row in set (0.00 sec)

mysql> select cast('123' as signed);
+---------------------+
| cast(123 as signed) |
+---------------------+
|                 123 |
+---------------------+
1 row in set (0.00 sec)


mysql> select cast('12300001111' as signed integer);
+-------------------------------------+
| cast(12300001111 as signed integer) |
+-------------------------------------+
|                         12300001111 |
+-------------------------------------+
1 row in set (0.00 sec)

mysql> select cast('123000011112222' as signed integer);
+-----------------------------------------+
| cast(123000011112222 as signed integer) |
+-----------------------------------------+
|                         123000011112222 |
+-----------------------------------------+
1 row in set (0.00 sec)

mysql> select cast('-123000011112222' as signed integer);
+------------------------------------------+
| cast(-123000011112222 as signed integer) |
+------------------------------------------+
|                         -123000011112222 |
+------------------------------------------+
1 row in set (0.00 sec)

mysql> select cast('-123000011112222.123' as signed integer);
+----------------------------------------------+
| cast(-123000011112222.123 as signed integer) |
+----------------------------------------------+
|                             -123000011112222 |
+----------------------------------------------+
1 row in set (0.00 sec)

mysql> select cast('-123000011112222.823' as signed integer);
+----------------------------------------------+
| cast(-123000011112222.823 as signed integer) |
+----------------------------------------------+
|                             -123000011112223 |
+----------------------------------------------+
1 row in set (0.00 sec)

double

mysql> select cast('-123002222.823' as double);
+----------------------------------+
| cast('-123002222.823' as double) |
+----------------------------------+
|                   -123002222.823 |
+----------------------------------+
1 row in set (0.00 sec)

mysql> select cast('-123000011112222.823' as double);
+----------------------------------------+
| cast('-123000011112222.823' as double) |
+----------------------------------------+
|                    -123000011112222.83 |
+----------------------------------------+
1 row in set (0.00 sec)

decimal

mysql> select cast('-123002222.823' as decimal);
+-----------------------------------+
| cast('-123002222.823' as decimal) |
+-----------------------------------+
|                        -123002223 |
+-----------------------------------+
1 row in set (0.00 sec)

mysql> select cast('-123002222.823' as decimal(10, 2));
+------------------------------------------+
| cast('-123002222.823' as decimal(10, 2)) |
+------------------------------------------+
|                             -99999999.99 |    -- 这个结果有问题
+------------------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> select cast('-123002222.823' as decimal(20, 2));
+------------------------------------------+
| cast('-123002222.823' as decimal(20, 2)) |
+------------------------------------------+
|                            -123002222.82 |
+------------------------------------------+
1 row in set, 1 warning (0.00 sec)

( 本文完 )