How to convert character types in mysql

MySQL is a popular relational database management system, which is mainly used to store and manage data. MySQL has a very rich data type, including character types. Character types play an important role in databases because they can be used to store information such as text, strings, and dates.

However, in actual use, we may encounter character type conversion problems. For example, convert a string to a number, or convert a date to another date format. In MySQL, character type conversion is very important because it allows us to process data more conveniently.

MySQL supports four character types: CHAR, VARCHAR, TEXT and BLOB. Among them, CHAR and VARCHAR are used to store strings, and TEXT and BLOB are used to store large text and binary data. The main difference between these four types is the amount of data they can store and how they store it.

In MySQL, we can use the CAST function and CONVERT function to achieve character type conversion. The CAST function converts a value to a specified data type, while the CONVERT function converts a value to a specified character set. Here is an example of converting a string to a number using the CAST function:

SELECT CAST('123' AS UNSIGNED);

In this example, we are converting the string '123' to an unsigned integer type. In actual use, we need to choose the conversion type according to the actual situation.

In MySQL, you can also use the STR_TO_DATE function to convert a string to date format. Here is an example of using the STR_TO_DATE function to convert a date string to a date type:

SELECT STR_TO_DATE('2021-10-01', '%Y-%m-%d');

In this example, we convert the date string '2021-10-01' to a date type. It is important to note that when converting date strings, you must use the correct format string.

In addition to the above functions, MySQL also supports forced type conversion. Enclose the variable or expression in parentheses, and add the data type to be converted before the parentheses. For example, to convert a string to an integer, you can use the following method:

SELECT (5 + '10');

In this example, we use brackets to enclose the string '10', and add the data type INT before the brackets, adding '10' is converted to integer type. Although this method is convenient, it should be noted that data type conversion may reduce query efficiency and accuracy.

In actual use, it is necessary to select the appropriate character type and conversion method according to the actual situation. If you are not sure how to deal with character type conversion issues, it is recommended to refer to the MySQL official documentation or consult a professional.

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