How can the field type be modified in SQL Server?

To change the data type of a field in a SQL Server table, you can use the ALTER TABLE statement. Here is an example:

-- 修改表中的字段类型
ALTER TABLE TableName
ALTER COLUMN ColumnName NewDataType

In the example above, you need to replace TableName with the name of the table you want to modify, ColumnName with the name of the field you want to modify, and NewDataType with the new data type you want to change the field to.

Please be aware that changing field types may result in data loss or truncation, so proceed with caution. It is recommended to test these changes before implementing them in a production environment.