Some 12C Features

Will try to describe some of the 12C features and will keep editing this post.

Note:

• If you want to install Oracle 12 on Windows 7, refer the steps here 
• To troubleshoot invalid common user or role name after installation, go here

Feature List

 Identity Columns:

• Also known as auto-number column. This implies that the data in the column should increase when data is inserted).
• Read article on the same here.

 Invisible Columns:

• Columns can be made invisible
• It gives one the ability to introduce a change while minimizing any negative side effects of that change.
• Read article on the same here 

With Clause:

• Instead of using a stored PL/SQL function, we can include the body of the function in the SQL query
• Read article on the same here 

 Truncate statements with the cascade option

• We could not truncate table with foreign key constraints.
• Now in 12c, one can execute the truncate table command with the cascade option (to cascade through the child tables).
• Note: You would need to create the foreign key with the "on delete cascade" option

Columns can have a default value in place of NULL

• You can define a column to have a default value when NULL is inserted
• e.g. create table ......  product_id NUMBER ON NULL 0,.....
• So if one explicity inserts NULL, it will be populated by value 0

Multiple Index - same columns

• You can create multiple indexes (different types) on a same set of columns.
• Assume you need to change from B*tree to Bitmap or vice versa.
• You need not drop the index.
• Just make the first index invisible and make a new index.
• Conditions:
• Different types of indexes
• Different uniqueness
• Different partitions are used

 

12 C Feature - WITH Clause

Note: Index article on some 12c features can be seen here

The with clause is more efficient to use than sub queries.
Instead of using a stored PL/SQL function, we can include the body of the function in the SQL query.
Benefit is that it will run faster than the call of a function by the same statement.

This can be better explained with an example.
Lets create a table with some test data.

Look at the usage of the function using with - in the body of the query.

The function in the with clause over-rides the function created at schema level. In below screenshot, you can see the schema level function returning SYSDATE+1 and the with clause function returning SYSDATE+2. Check the output - its SYSDATE+2.

Note: You need to put in a slash (/) at the end else SQLPLUS waits for more input (refer lines 9-12 in the snapshot waiting when ENTER key was pressed).