DB2 alter table Field

DB2 alter: Add/delete/Reset Column

1. Add Fields

Alter table [table_name] add [column_name] [column_type]

2. Change the field type

Alter table [table_name] alter column [column_name] Set Data Type [column_type]

Note: There are restrictions on changing the field type. For example, you can change the field to be larger than the previous type length. to change it to a smaller value or modify the decimal point length, you must drop the original column first, and then add again.

For example, I want to change the column of A varchar (10) To varchar (6) or change the column of a decimal (16, 2) to decimal (16, 4, you cannot use the preceding statement to modify the column type. You must drop the column type first.

3. Remove Fields

Alter table [table_name] Drop column [column_name]

Note: After dropping a field, you may not be able to execute the Table query/insert operation. You Need To reorg the table.

4. Add default values for fields

Alter table [table_name] alter column [column_name] Set default [value]

5. Add fields with default values

Alter table [table_name] add column [column_name] [column_type] not null with default [value]

6. Set the default field time to the current time.

Alter table [table_name] alter column [column_name] Set default current date;