to_char函数将number转为string
时间: 2023-09-01 17:01:42 浏览: 195
to_char函数是Oracle数据库提供的一个函数,可以将number类型的数据转换为string类型。
使用to_char函数的语法如下:
to_char(number, format)
其中,number是要转换的数字,可以是一个实数或者整数;
format是一个字符串,用于指定数字转换的格式,在格式中可以使用一些特殊字符来指定转换的格式,比如数字的位数、小数的位数、货币符号等。
具体使用示例:
假设有一个number类型的变量num,它的值为12345.6789,我们想将它转换为string类型并保留两位小数,可以使用以下语句:
result := to_char(num, 'FM99999.99');
其中,FM代表前导零,99999表示数字的位数,.99表示小数的位数。
执行这个语句后,result的值将是"12345.68",即将num转换为string类型并保留两位小数。
总之,to_char函数可以将number类型的数据转换为string类型,并且可以指定转换的格式,非常灵活和方便。
相关问题
mysql to_char函数用法
抱歉,MySQL中没有to_char函数。to_char函数是Oracle数据库中的一个函数,用于将日期或数字类型的数据转换为字符类型。在MySQL中,要将日期或数字转换为字符类型,可以使用DATE_FORMAT函数或CAST函数。
1. 使用DATE_FORMAT函数将日期类型转换为字符类型:
```sql
SELECT DATE_FORMAT(date_column, 'format_string') AS formatted_date
FROM your_table;
```
其中,date_column是你要转换的日期列,format_string是你指定的日期格式。例如,要将日期转换为YYYY-MM-DD格式:
```sql
SELECT DATE_FORMAT(date_column, '%Y-%m-%d') AS formatted_date
FROM your_table;
```
2. 使用CAST函数将数字类型转换为字符类型:
```sql
SELECT CAST(number_column AS CHAR) AS string_number
FROM your_table;
```
其中,number_column是你要转换的数字列。例如,将整数列转换为字符类型:
```sql
SELECT CAST(number_column AS CHAR) AS string_number
FROM your_table;
```
请根据你的具体需求选择适合的函数和格式。
void Dis_menu() { if(menu == 0) { LCD_Clear(); LCD_Write_String(0,0,"00:00:00"); LCD_Write_String(0,1,"00-00 Hum: %"); } else if(menu == 1) { LCD_Clear(); LCD_Write_String(0,0," Set time "); LCD_Write_String(0,1,"00-00 00:00:00 "); LCD_Write_Char(0,1,yue/16%16+0x30);LCD_Write_Char(1,1,yue%16+0x30); LCD_Write_Char(3,1,ri/16%16+0x30);LCD_Write_Char(4,1,ri%16+0x30); LCD_Write_Char(6,1,shi/16%16+0x30);LCD_Write_Char(7,1,shi%16+0x30); LCD_Write_Char(9,1,fen/16%16+0x30);LCD_Write_Char(10,1,fen%16+0x30); LCD_Write_Char(12,1,miao/16%16+0x30);LCD_Write_Char(13,1,miao%16+0x30); } else if(menu ==6) { LCD_Clear(); LCD_Write_String(0,0," Set chun "); LCD_Write_String(0,1," 00-00-00 S: "); LCD_Write_Char(1,1,A_shi/16%16+0x30);LCD_Write_Char(2,1,A_shi%16+0x30); LCD_Write_Char(4,1,A_fen/16%16+0x30);LCD_Write_Char(5,1,A_fen%16+0x30); LCD_Write_Char(7,1,A_miao/16%16+0x30);LCD_Write_Char(8,1,A_miao%16+0x30); LCD_Write_Number(13,1,shui1*10,3); } else if(menu ==10) { LCD_Clear(); LCD_Write_String(0,0," Set xia "); LCD_Write_String(0,1," 00-00-00 S: "); LCD_Write_Char(1,1,B_shi/16%16+0x30);LCD_Write_Char(2,1,B_shi%16+0x30); LCD_Write_Char(4,1,B_fen/16%16+0x30);LCD_Write_Char(5,1,B_fen%16+0x30); LCD_Write_Char(7,1,B_miao/16%16+0x30);LCD_Write_Char(8,1,B_miao%16+0x30); LCD_Write_Number(13,1,shui2*10,3); } else if(menu ==14) { LCD_Clear(); LCD_Write_String(0,0," Set qiu "); LCD_Write_String(0,1," 00-00-00 S: "); LCD_Write_Char(1,1,C_shi/16%16+0x30);LCD_Write_Char(2,1,C_shi%16+0x30); LCD_Write_Char(4,1,C_fen/16%16+0x30);LCD_Write_Char(5,1,C_fen%16+0x30); LCD_Write_Char(7,1,C_miao/16%16+0x30);LCD_Write_Char(8,1,C_miao%16+0x30); LCD_Write_Number(13,1,shui3*10,3); } else if(menu ==18) { LCD_Clear(); LCD_Write_String(0,0," Set dong "); LCD_Write_String(0,1," 00-00-00 S: "); LCD_Write_Char(1,1,D_shi/16%16+0x30);LCD_Write_Char(2,1,D_shi%16+0x30); LCD_Write_Char(4,1,D_fen/16%16+0x30);LCD_Write_Char(5,1,D_fen%16+0x30); LCD_Write_Char(7,1,D_miao/16%16+0x30);LCD_Write_Char(8,1,D_miao%16+0x30); LCD_Write_Number(13,1,shui4*10,3); } else if(menu ==22) { LCD_Clear(); LCD_Write_String(0,0,"Hum_L:"); LCD_Write_Number(6,0,hum_l,3); } } 对这段代码进行逐条注释
```c++
void Dis_menu() { //定义函数Dis_menu
if(menu == 0) { //如果当前菜单为0
LCD_Clear(); //清空LCD显示
LCD_Write_String(0,0,"00:00:00"); //在第0行第0列写入"00:00:00"
LCD_Write_String(0,1,"00-00 Hum: %"); //在第1行第0列写入"00-00 Hum: %"
} else if(menu == 1) { //如果当前菜单为1
LCD_Clear(); //清空LCD显示
LCD_Write_String(0,0," Set time "); //在第0行第0列写入" Set time "
LCD_Write_String(0,1,"00-00 00:00:00 "); //在第1行第0列写入"00-00 00:00:00 "
LCD_Write_Char(0,1,yue/16%16+0x30);LCD_Write_Char(1,1,yue%16+0x30); //在第1行第0列写入月份的十位数和个位数
LCD_Write_Char(3,1,ri/16%16+0x30);LCD_Write_Char(4,1,ri%16+0x30); //在第1行第3列写入日期的十位数和个位数
LCD_Write_Char(6,1,shi/16%16+0x30);LCD_Write_Char(7,1,shi%16+0x30); //在第1行第6列写入小时的十位数和个位数
LCD_Write_Char(9,1,fen/16%16+0x30);LCD_Write_Char(10,1,fen%16+0x30); //在第1行第9列写入分钟的十位数和个位数
LCD_Write_Char(12,1,miao/16%16+0x30);LCD_Write_Char(13,1,miao%16+0x30); //在第1行第12列写入秒钟的十位数和个位数
} else if(menu ==6) { //如果当前菜单为6
LCD_Clear(); //清空LCD显示
LCD_Write_String(0,0," Set chun "); //在第0行第0列写入" Set chun "
LCD_Write_String(0,1," 00-00-00 S: "); //在第1行第0列写入" 00-00-00 S: "
LCD_Write_Char(1,1,A_shi/16%16+0x30);LCD_Write_Char(2,1,A_shi%16+0x30); //在第1行第1列写入春季开始时间的小时的十位数和个位数
LCD_Write_Char(4,1,A_fen/16%16+0x30);LCD_Write_Char(5,1,A_fen%16+0x30); //在第1行第4列写入春季开始时间的分钟的十位数和个位数
LCD_Write_Char(7,1,A_miao/16%16+0x30);LCD_Write_Char(8,1,A_miao%16+0x30); //在第1行第7列写入春季开始时间的秒钟的十位数和个位数
LCD_Write_Number(13,1,shui1*10,3); //在第1行第13列写入水位的值
} else if(menu ==10) { //如果当前菜单为10
LCD_Clear(); //清空LCD显示
LCD_Write_String(0,0," Set xia "); //在第0行第0列写入" Set xia "
LCD_Write_String(0,1," 00-00-00 S: "); //在第1行第0列写入" 00-00-00 S: "
LCD_Write_Char(1,1,B_shi/16%16+0x30);LCD_Write_Char(2,1,B_shi%16+0x30); //在第1行第1列写入夏季开始时间的小时的十位数和个位数
LCD_Write_Char(4,1,B_fen/16%16+0x30);LCD_Write_Char(5,1,B_fen%16+0x30); //在第1行第4列写入夏季开始时间的分钟的十位数和个位数
LCD_Write_Char(7,1,B_miao/16%16+0x30);LCD_Write_Char(8,1,B_miao%16+0x30); //在第1行第7列写入夏季开始时间的秒钟的十位数和个位数
LCD_Write_Number(13,1,shui2*10,3); //在第1行第13列写入水位的值
} else if(menu ==14) { //如果当前菜单为14
LCD_Clear(); //清空LCD显示
LCD_Write_String(0,0," Set qiu "); //在第0行第0列写入" Set qiu "
LCD_Write_String(0,1," 00-00-00 S: "); //在第1行第0列写入" 00-00-00 S: "
LCD_Write_Char(1,1,C_shi/16%16+0x30);LCD_Write_Char(2,1,C_shi%16+0x30); //在第1行第1列写入秋季开始时间的小时的十位数和个位数
LCD_Write_Char(4,1,C_fen/16%16+0x30);LCD_Write_Char(5,1,C_fen%16+0x30); //在第1行第4列写入秋季开始时间的分钟的十位数和个位数
LCD_Write_Char(7,1,C_miao/16%16+0x30);LCD_Write_Char(8,1,C_miao%16+0x30); //在第1行第7列写入秋季开始时间的秒钟的十位数和个位数
LCD_Write_Number(13,1,shui3*10,3); //在第1行第13列写入水位的值
} else if(menu ==18) { //如果当前菜单为18
LCD_Clear(); //清空LCD显示
LCD_Write_String(0,0," Set dong "); //在第0行第0列写入" Set dong "
LCD_Write_String(0,1," 00-00-00 S: "); //在第1行第0列写入" 00-00-00 S: "
LCD_Write_Char(1,1,D_shi/16%16+0x30);LCD_Write_Char(2,1,D_shi%16+0x30); //在第1行第1列写入冬季开始时间的小时的十位数和个位数
LCD_Write_Char(4,1,D_fen/16%16+0x30);LCD_Write_Char(5,1,D_fen%16+0x30); //在第1行第4列写入冬季开始时间的分钟的十位数和个位数
LCD_Write_Char(7,1,D_miao/16%16+0x30);LCD_Write_Char(8,1,D_miao%16+0x30); //在第1行第7列写入冬季开始时间的秒钟的十位数和个位数
LCD_Write_Number(13,1,shui4*10,3); //在第1行第13列写入水位的值
} else if(menu ==22) { //如果当前菜单为22
LCD_Clear(); //清空LCD显示
LCD_Write_String(0,0,"Hum_L:"); //在第0行第0列写入"Hum_L:"
LCD_Write_Number(6,0,hum_l,3); //在第0行第6列写入湿度低值的值
}
}
```
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