...
This essay developed out of conversations I've had with several other programmers about why Java smelled suspicious. It's not a critique of Java!
Sycorax - complete tutorials
Programming Tutorials
" Java provides the industry - software companies and customer alike , an opportunity to create a true open computing environment where software is portable,
and customers benefit from increase competition. "
Java and the Future
December 1, 2008-LEJB 3.1: EJB New and Improved!
The EJB 3.0 specification was a huge improvement from what you were used to in the early versions of EJB. Available as an early draft, EJB 3.1 has many more features and is even easier to use.
December 1, 2008-Should Java Assert that Network I/O Can't Occur on the UI Thread?
Doing network I/O on the user interface (UI) thread is bad. Most developers know that and can tell you why; unfortunately, it's still done.
Register now to recieve special alert and latest technology news!
Oracle Interview Question
What is the difference between primary key and unique constraint?
Ans: If we declared a column as primary key it will take only unique values. But if we declared a column as unique key it will take either unique or null values.
What is index?
Ans: It is a database object. It is used to speed up the retrieval process.
What is composite unique key?
Ans: If no single column uniquely identifies occurrences within a table, then combining multiple is used to create a unique identifier for the table is known as composite unique key.
When do we create index?
Ans: suppose there is a table, which stores large amount of data. Then we need to speed up the retrieval process. That's why we create an index.
Index helps to retrieve the data in faster way.
When do we require to drop existing index?
Ans: we drop an index when the table is small and the table is updated/inserted frequently.
If the database is frequently updated or inserted (Transactional Database) then index will slow down the data entry as index creation takes some time. If the database is not frequently updated (OLAP online analytical processing - data warehouse) and it is required to retrieve the data often compared the data entry then only we will use index.
What are the different types of index available in oracle? Give definition?
Ans: B-tree indexes-the default and the most common
B-tree cluster indexes-defined specifically for cluster
Hash cluster indexes-defined specifically for a hash cluster
Global and local indexes-relate to partitioned tables and indexes
Reverse key indexes-most useful for Oracle Real Application Cluster
applications
Bitmap indexes-compact; work best for columns with a small set of values
Function-based indexes-contain the precomputed value of a
function/expression
Domain indexes-specific to an application or cartridge.
When do we go for bitmap index?
Ans: When there is a table, which has a column like name. Name column contains a small set of values then we create a bitmap index. It's mainly useful for datawarehouseing.
When a table has millions of rows and key columns have low cardinality.
When there is read only or low update activity on the key column.
