Create a PrimaryKey on existing table without unique values
lets assume that there was a table ABC that was already existing in the database and you want to add an additional column with unique primary key values. sql to create table ABC : CREATE TABLE "ABC" ( "USERNAME" VARCHAR2(30 BYTE) NOT NULL ENABLE, "USER_ID" NUMBER NOT NULL ENABLE, "CREATED" DATE NOT NULL ENABLE ) TABLESPACE "USERS" ; Now we can add an additional column ID which will be populated with all unique values for PrimaryKey. alter table abc add(ID NUMBER); We will now create a sequence and get the values from the seq and insert them into table ABC new ID column: CREATE SEQUENCE SEQ_ID START WITH 1 INCREMENT BY 1 MAXVALUE 999999 MINVALUE 1 NOCYCLE; Now insert the unique values into the database with below sql: UPDATE abc SET ID = SEQ_ID.NEXTVAL; now you can add unique constraint (or) add primary key constraint to table,so that it wont take any more duplicate value into the table. alter ...
