MySQL Add Column: Set Default Value

To add a field and assign a value in MySQL, you can use the ALTER TABLE statement.

Assume there is a table called table_name, and we need to add a field called column_name, setting a default value for all existing rows.

Here are the specific steps:

1. First, add a new field using the following statement:
2. Add a new column with a specific data type to the specified table.
3. “table_name” is the name of the table where the field will be added, “column_name” is the name of the field to be added, and “datatype” is the data type of the field.
4. For example, to add a field named email to a table named users, you can use the following statement:
5. Add a column called “email” with a data type of VARCHAR(255) to the table named “users”.
6. Next, set the default value for the new field using the following statement:
7. Update the table by setting the column to a default value.
8. “table_name is the name of the table to be updated, column_name is the name of the field to be updated, and default_value is the default value to be set for the field.”
9. For example, to set a default value of ‘example@example.com’ for a field named email, you can use the following statement:
10. Update the users’ email to ‘example@example.com’ in the database.
11. Note: if the new field allows for null values, there is no need to set a default value.

After completing the steps above, a new field will be added to the table, and all existing rows will be assigned default values.