SQL

alter table oracle

ALTER TABLE tablename MODIFY columnname varchar2(100)

alter table oracle

ALTER TABLE products
ADD CONSTRAINT fk_supplier
  FOREIGN KEY (supplier_id)
  REFERENCES supplier(supplier_id);

alter table oracle

ALTER TABLE table_name
ADD CONSTRAINT constraint_name
   FOREIGN KEY (column1, column2, ... column_n)
   REFERENCES parent_table (column1, column2, ... column_n);

oracle alter table

ALTER TABLE table_name 
ADD column_name data_type constraint;
Code language: SQL (Structured Query Language) (sql)