Showing posts from November, 2011

Which perform faster in Oracle Database IN or EXISTS

EXISTS is always perform faster in Oracle Database because “EXISTS” returns a boolean value (True or False), whereas “IN” returns a value.

Oracle Solaris 11 releases with new features

Oracle Solaris 11 will be officially released today, including the Sparc platform compatible with x86.

Oracle Solaris 11 is SPARC SuperCluster T4-4 Integrated Systems and Oracle SPARC T4 server product line operating system, its also supports Oracle Exadata Database cloud server X2-2, X2-8 system, middleware and Oracle Exalogic cloud server.

How many LONG columns are allowed in a table in Oracle Database

Restriction for the use of LONG columns in Oracle Databsae

1) Only one column of type LONG is allowed.

What is the difference between CLOB and BFile in Oracle Database

The Oracle BFile type, is used to store unstructured binary data outside of the database in the operating system. BFiles are read-only and only support random-reads.

CLOB type is stored in the database using two byte code character set. Unlike BFile, CLOB support sequential access and can be modified.

What is the difference between implicit and explicit cursor in Oracle Database

Whenever we issue an INSERT, DELETE, UPDATE or single row SELECT INTO statement, Oracle creates a implicit cursor to deal with this operation.

An explicit cursor, is a cursor in which the cursor name is explicitly assigned to a SELECT statement via the CURSOR … IS  statement.

What is the difference between truncate and delete in Oracle Database

TRUNCATE is much faster than delete because it does not allow for rollbacks to occur, and automatically commits data when finishes.Also truncate does not fire any trigger, so if there is a trigger on your table, TRUNCATE would not fire it but DELETE will and you cannot use the WHERE clause on TRUNCATE.

What is the DUAL table in Oracle Database

The DUAL table is a table that Oracle creates with it is data dictionary consisting in exactly one row. DUAL belongs to the SYS user but all users can query it , and use it’s unique property of returning only one row, to select pseudo-columns .