oracle add/modify/delete database field SQL

To add, modify, or delete multiple columns, separate them with commas.

1. Create the table structure:
create table test1

(id   INTEGER  not null，

name  varchar2(20) );

2. The syntax for adding fields: alter table tablename add (column datatype [default value][null/not null],….);

Example: alter table table name  add ( field name    data format);

 Modify comments: comment on column table name. field name is 'comment content';

3. The syntax of modifying the field: alter table tablename modify (column datatype [default value][null/not null],….);

Fourth, delete the field syntax: alter table tablename drop (column);

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