How to convert mysql character type

MySQL is a popular relational database management system that can handle a variety of data types. When we create a table in MySQL, we often need to specify the data type for each column. In some cases, we need to convert some kind of data to other types, such as converting character type to numeric type and vice versa. In this article, we will explore the methods of character type conversion in MySQL.

Data type

In MySQL, common character types include VARCHAR, CHAR and TEXT. VARCHAR is a variable-length string type, CHAR is a fixed-length string type, and TEXT is a type used to store large text. These types of data can store numeric and alphabetic characters but cannot perform mathematical calculations. Therefore, we need to convert them to numeric types such as INT or FLOAT.

Conversion method

MySQL provides several methods for converting character types to numeric types, each method is suitable for different situations. The following are some commonly used methods:

1. Use the CAST function

The CAST function is a function that converts one data type to another data type. For example, we can use the CAST function to convert VARCHAR type to INT type as follows:

SELECT CAST('123' AS UNSIGNED);

This query will return the integer 123. In this example, we convert the string '123' to an unsigned integer. We can also use the CAST function to convert other data types to INT, such as DATE and TIME types.

2. Use the CONVERT function

The CONVERT function is similar to the CAST function and can convert one data type to another data type. However, it can work with more data types. For example, we can use the CONVERT function to convert the DATETIME type to the VARCHAR type as follows:

SELECT CONVERT(NOW(), VARCHAR);

This query will return the string representation of the current date and time. In this example, we convert DATETIME type to VARCHAR type.

3. Use the 0 operator

The 0 operator can convert the string type to a numeric type. For example, we can convert VARCHAR type to INT type using the 0 operator as follows:

SELECT '123'+0;

This query will return the integer 123. In this example, we convert the string '123' to an integer type.

4. Use *1 operator

Similar to 0 operator, 1 operator can also convert string type to numeric type. For example, we can convert the VARCHAR type to the FLOAT type using the 1 operator as follows:

SELECT '1.23'*1;

This query will return the floating point number 1.23. In this example, we convert the string '1.23' to a float type.

Notes

When performing character type conversion, you need to pay attention to the following points:

• Make sure that the string to be converted contains the correct number format. For example, if a string contains characters other than numbers, the conversion will fail.
• The converted data type may lose some information other than numbers. For example, converting a VARCHAR type to an INT type removes all fractional parts.
• The converted results may result in data loss or inaccuracy. For example, converting a LONGTEXT type to an INT type may result in data truncation.

Conclusion

MySQL provides several methods to convert character types to numeric types, including using the CAST function, CONVERT function, 0 operator and *1 operator. When converting character types, you need to pay attention to the data format, data type, and data correctness to ensure that the converted data is accurate.

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