In other DBs it looks like:
in MySQL : ID int NOT NULL AUTO_INCREMENTPreviously in Oracle to have an ID column that starts with 1 and increments one by one for each new record we need to create a sequence and a trigger to assign a number from sequence to column for each insert query. However, with IDENTITY we can alter a column as auto increment identity. For example:
in MS SQL : ID int IDENTITY(1,1) PRIMARY KEY
in Access : ID Integer PRIMARY KEY AUTOINCREMENT
CREATE TABLE ATK_test_tNow, by just an insert and without mentioning "id" column in the insert, it will get 1 for the first row and 2 for the second insert.
( id NUMBER GENERATED ALWAYS AS IDENTITY, name VARCHAR2(255) );
INSERT INTO ATK_test_t (name) VALUES ('First Name');and the result will be:
INSERT INTO ATK_test_t (name) VALUES ('Second Name'),(;Third Name');
SQL> SELECT * FROM ATK_test_t;
ID NAMEThis new Identity function has three types of:
1 First Name
2 Second Name
3 Third Name
- ALWAYS: It gets number, and you do not allow to assign any other number in insert or pass null to this column ( generate error ORA-32795)
- DEFAULT: We can assign or update any number but cannot assign Null
- DEFAULT ON NULL: We can assign Null, but Oracle will assign next number for its value.