mysql convert numbers

In Mysql operations, numbers sometimes need to be converted, which is a very common operation when performing data calculations and table analysis. This article will introduce common number type conversion methods to help Mysql users perform number conversion more conveniently.

1. Convert a number to a string

The method to convert a number to a string is to use the CAST() function or CONVERT() function. The CAST() function can convert numbers to any data type, while the CONVERT() function can specify a specific string type.

For example, suppose you want to convert the number 123 to a string:

SELECT CAST(123 AS CHAR);

or

SELECT CONVERT(123, CHAR);

Running the above code will output the string number "123" .

2. Convert a string to a number

In contrast to converting a number to a string, the method of converting a string to a number also uses the CAST() function or CONVERT( )function. It should be noted that when performing string conversion, you need to ensure that the content in the string can indeed be converted into numbers, otherwise an error will occur.

For example, suppose you want to convert the string "456" to a number:

SELECT CAST("456" AS SIGNED);

or

SELECT CONVERT("456", SIGNED);

The SIGNED data type is used here because the string "456" is a positive number. If you want to convert negative numbers to numbers, you can use SIGNED or UNSIGNED data types.

3. Convert hexadecimal string to number

In Mysql, you can also convert hexadecimal string to number. Use the CONV() function to convert a hexadecimal string to any other base number.

For example, suppose you want to convert the hexadecimal string "FF" to a decimal number:

SELECT CONV("FF", 16, 10);

This code will return 255, which is the hexadecimal string "FF" Decimal value.

4. Retain numbers to a specified number of decimal places

In Mysql, you can use the ROUND() function to retain a number to a specified number of decimal places. The second parameter of the ROUND() function specifies the number of decimal places.

For example, let's say you want the number 3.14159 to two decimal places:

SELECT ROUND(3.14159, 2);

This code will return 3.14, the number 3.14159 to two decimal places.

5. Specifying Numbers in Scientific Notation

Sometimes when a number is too large or too small, using scientific notation can represent the number more visually. In Mysql, you can use the FORMAT() function to specify a number in scientific notation. The second parameter of the FORMAT() function specifies the number of decimal places to be displayed.

For example, suppose you want to specify the number 9999999999 in scientific notation:

SELECT FORMAT(9999999999, "0.00E0");

This code will return 1.00E10, which is the result of the number 9999999999 specified in scientific notation.

In general, numeric type conversion is a very common operation in Mysql. This article describes common number type conversion methods, including converting a number to a string, converting a string to a number, converting a hexadecimal string to a number, retaining a number to a specified number of decimal places, and specifying a number as scientific counting method. These operations will be very useful when performing data calculations and table analysis.

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