SQL ADD COLUMN: Adding Fields & Values

To add a new field and assign a value in SQL, you can use the ADD COLUMN clause in the ALTER TABLE statement. Here are some commonly used methods:

1. Add new columns to the existing table and specify default values:
2. Add a new column with a specified data type and default value to the specified table.
3. Add new columns to the existing table and set specific values for the existing rows.
4. Add a new column with a specified data type to the table name;
   Update the table name and set the new column to a specific value.
5. Add new columns to the existing table and fetch values from another table.
6. Add a new column of specified data type to the table named “表名” and update it by selecting data from another table that meets specified conditions.

Please note that these methods all require modifying the existing table, so please be sure to backup your data or proceed with caution before making any changes.