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The Identity column is new to Oracle 12c, and this article explains what it is for and how to use it.
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Have you ever needed to generate a unique value for a column, and have it automatically set when you insert a new value?
In other databases, this is simple, but in Oracle, it was a little complicated - until Oracle 12c.
The Problem
Let's say you wanted to have a unique value generated for a column, such as a primary key value. You wanted this value to be automatically generated when you insert a new record, without having to specify it.
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If you've used other databases, such as MySQL, this was easy to do. You would just define a column as AUTO_INCREMENT, and whenever you insert a new record, you would leave this column out of the INSERT statement, and the new value would be automatically set.
However, the only way to do this in Oracle is to use a combination of a sequence and a trigger on the table. (LINK)
Until Oracle 12c.
What is an Identity Column in Oracle?
Oracle 12c has introduced the concept of an IDENTITY column. You can set a column as an identity, which works in a similar way to the auto increment column.
Generate key for google maps api v2 version. Then, whenever you insert a new record into the table, you don't need to specify a value for this column, as it will be generated automatically.
It's a great way to ensure a value is always unique in a column, and to make sure that whoever inserts a record doesn't need to manually call a sequence. Free office 2010 activation key.
3 Steps total
Step 1: Create table with an Identity column
To set up an identity column, you need to do it as part of the CREATE TABLE or ALTER TABLE statements.
For example:
CREATE TABLE idtest (
new_id NUMBER GENERATED AS IDENTITY,
first_name VARCHAR2(100)
last_name VARCHAR2(100)
);
new_id NUMBER GENERATED AS IDENTITY,
first_name VARCHAR2(100)
last_name VARCHAR2(100)
);
This means that the new_id column is now an identity column.
If you want to set an existing column as an identity column, I would advise against it. It could cause issues with your data. The better way to do this would be to create a new table and use some renaming of tables to get this done.
Just like with a sequence, you can specify different values and parameters for an identity column.
Let's say you wanted to start your values at 1000, and increment by 5 every time. You can do this in your CREATE TABLE statement:
CREATE TABLE idtest2 (
new_id NUMBER GENERATED AS IDENTITY (START WITH 1000 INCREMENT BY 5)
testval VARCHAR2(50)
);
new_id NUMBER GENERATED AS IDENTITY (START WITH 1000 INCREMENT BY 5)
testval VARCHAR2(50)
);
Whenever you insert new values, they will start at 1000 and go up by 5 (1000, 1005, 1010, 1015).
Step 2: Insert new records into the table
So, now you have set up the identity column, it's time to use it.
To use an identity column, you just run an INSERT statement that does not use this column.
INSERT INTO idtest (first_name, last_name) VALUES (‘Peter’, ‘Parker’);
INSERT INTO idtest (first_name, last_name) VALUES (‘Clark’, ‘Kent’);
INSERT INTO idtest (first_name, last_name) VALUES (‘Bruce’, ‘Wayne’);
INSERT INTO idtest (first_name, last_name) VALUES (‘Clark’, ‘Kent’);
INSERT INTO idtest (first_name, last_name) VALUES (‘Bruce’, ‘Wayne’);
Each of these statements will insert a new value in the idtest table. Notice how I did not specify a value for the new_id column.
Step 3: Query table to see that values have been set
Now, to check that the values have been inserted, we can query the table.
SELECT new_id, first_name, last_name
FROM idtest;
SELECT new_id, first_name, last_name
FROM idtest;
You can see that the records exist and that the new_id has been set.
Published: Aug 16, 2016 · Last Updated: Nov 04, 2016
References
- The Full List - Oracle 12c New Features for Developers