oracle 12c new features for developers
TRANSCRIPT
Oracle 12c New Features for Developers
By Complete IT Professional
www.completeitprofessional.com
Oracle 12c
• Released in 2013
• Contains a lot of new features
• Some are useful for DBAs, some are useful for developers, some for both
• As a developer, what do you need to know?
• I wrote an entire post on it:
http://www.completeitprofessional.com/oracle-12c-new-features-for-developers
• These slides explain all of those features
Increased column size limits
• VARCHAR2, NVARCHAR2, and RAW are larger than previous Oracle versions
Data Type Oracle 11g
Limit
Oracle 11g
PL/SQL Limit
Limit in
Oracle 12c
VARCHAR2 2K 4K 32K
NVARCHAR2 2K 4K 32K
RAW 2K 4K 32K
Increased column size limits
• How can you use the new sizes?
• Change the setting called MAX_STRING_SIZE within the init.orafile
• STANDARD – old sizes
• EXTENDED – new sizes
APPROX_COUNT_DISTINCT
• New function – APPROX_COUNT_DISTINCT
• Gives you an approximate count of records
• Faster than COUNT
• Not 100% accurate but pretty close
Row Limiting with Top N
• Getting the top N rows can be hard in Oracle
• In Oracle 12c, you can use new syntax
• FETCH FIRST 10 ROWS ONLY – shows only the first 10 rows
Row Limiting with Top N
SELECT first_name, last_name, date_of_birth
FROM student
ORDER BY date_of_birth
FETCH FIRST 10 ROWS ONLY;
Pattern Matching
• Pattern matching is easier in Oracle 12c
• Uses the MATCH_RECOGNIZE keyword
Pattern Matching Syntax
SELECT columns
FROM table
MATCH_RECOGNIZE (
PARTITION BY ...
ORDER BY ...
MEASURES ...
PATTERN...
DEFINE...
)
ORDER BY col1...
JSON in Database
• Oracle 12c now support JSON in database columns
• You can query directly inside the column data
JSON Example{
“businessName”:”Cars Galore”,
“address”:{
“streetNumber”:”14”,
“streetName”:”Main Street”,
“city”:”Denver”,
“state”:”Colorado”,
“country”:”USA”},
“businessIndustry”:”Automotive”
}
SELECT
b.document.businessName,
b.document.address.streetNumber,
b.document.address.streetName
FROM businesses b
Lateral Clause for Inline Views
• Normally you can’t refer to columns outside an inline view from within the inline view
• With a LATERAL clause, you can
Lateral Clause Example
SELECT first_name, last_name, school_name
FROM student s,
LATERAL (SELECT school_name
FROM school sc
WHERE sc.school_id = s.school_id)
CROSS APPLY Clause
• Similar to Lateral
• Variant of the CROSS JOIN
• Right side of the keyword can reference the column on the left
CROSS APPLY Example
SELECT first_name, last_name, school_id, school_name
FROM student s,
CROSS APPLY (SELECT school_name
FROM school sc
WHERE sc.school_id = s.school_id
AND sc.school_state = ‘California’)
OUTER APPLY Clause
• Similar to CROSS APPLY
• More like a LEFT OUTER JOIN
OUTER APPLY Example
SELECT first_name, last_name, school_id, school_name
FROM student s,
OUTER APPLY (SELECT school_name
FROM school sc
WHERE sc.school_id = s.school_id
AND sc.school_state = ‘California’)
Partial Join Evaluation
• New optimisation type
• Part of the optimisation process
• You might see it in the Explain Plan
• Partial Join Evaluation
• Also called PJE
Cascading Truncate
• Have you tried to TRUNCATE a table that had other records referring to it, and got an error about foreign keys?
• With Oracle 12c, you can run a TRUNCATE CASCADE
• This will skip this error and delete the rows that refer to it
• Only works if the foreign key is defined as ON DELETE CASCASE
Cascading Truncate Example
TRUNCATE TABLE parent_table_name CASCADE;
Pluggable Databases
• One of the main features in Oracle 12c
• A “root” database is created
• “Seed” database is a template for creating other databases
• “Pluggable databases” are where the data is stored
• All inside the root
Why pluggable databases?
• Easier maintenance
• Easier implementation of new databases – just copy the seed
• Easier to move to the cloud
Invisible Columns
• Columns that do not appear in the table definition or SELECT * statements
• Use the INVISIBLE keyword when defining a column
Invisible Indexes
• Allows more than one index on a column at one time
• Create index and add the INVISIBLE keyword
Identity Columns
• Set a column to automatically generate a value
• Similar to AUTO_INCREMENT in other databases
• Add GENERATED AS IDENTITY to column definition when creating a table
Default Values
• Simplify data entry
• Use sequences as the default values
• Or use default values only when a NULL is specified
Session Sequences
• Sequences currently keep their values for the database for all sessions
• Session sequences are new
• They let you retain the value only for the session
• Not very useful for primary keys, but there are other uses
Sequence KEEP and NOKEEP
• KEEP and NOKEEP are keywords for creating sequences
• KEEP retains the NEXTVALUE value for replays during Application Continuity
• NOKEEP will not retain the NEXTVALUE for these replays
• NOKEEP is the default
Data Redaction
• You can hide certain fields in certain ways
• Replace characters with spaces or numbers
• Or, change part of the information
• Good security feature
Grant Roles to PL/SQL Programs Only
• Previously, you had to grant user access to the PL/SQL program and the table
• Now, just grant user access to the PL/SQL program
• Program will still access the table
• Makes it more secure
UTL_CALL_STACK Package
• Improvements to the call stack
• Use the UTL_CALL_STACK package to get information about your call stack
PL/SQL ACCESSIBLE BY Clause
• Allows you to specify which packages can access other packages
• Helps with security
• Simplifies package definition if you want to implement this
• Add the words ACCESSIBLE BY to the package when defining
PL/SQL Table Operator
• Before 12c, you could only use the TABLE operator in some situations
• Now, you can use them with locally defined types
WITH Clause and PL/SQL Functions
• Now you can define PL/SQL functions and procedures inside a WITH clause
• Likely improves run time
• Object is not created and stored in the database
Online DDL Statements
• DDL normally locks tables
• Some statements can now be run in “online” mode, which does not impact any DML that is running
• Statements relate to indexes, constraints, and columns
DDL Logging
• You can enable DDL logging
• Many DDL statements are captured
• CREATE/ALTER/DROP/TRUNCATE TABLE
• CREATE/ALTER/DROP PACKAGE/FUNCTION/VIEW/SYNONYM/SEQUENCE
• DROP USER
Bequeath Option
• Allows you to specify which user’s privileges will be used when running a statement
• Specify either invoker’s or definer’s rights
• Invoker’s rights – the person running the statement
• Definer’s rights – the person who created the object
Period Definition
• Allows you to easily specify which records are valid at a particular date
• Use the PERIOD clause when creating a table
• You can then use the PERIOD clause in SELECT queries
Conclusion
• Many new features in Oracle 12c
• These are all of the features I think are helpful for new developers
• Find out more here:
http://www.completeitprofessional.com/oracle-12c-new-features-for-developers