How can I change the field type length in MySQL?

To change the type and length of a MySQL field, you can use the ALTER TABLE statement.

Here is an example of changing the type of a field in a table from VARCHAR(100) to VARCHAR(255):

ALTER TABLE 表名 MODIFY 列名 VARCHAR(255);

In this case, “table name” refers to the name of the table to be modified, “column name” refers to the name of the field to be modified, and “VARCHAR(255)” represents the new data type and length of the field.

Caution: When executing the ALTER TABLE statement, make sure there is no data in the table or the data has been backed up, as changing the field type and length may result in data loss or truncation.