What is object data type in oracle?
New/User defined objects can be created from any database built in types or by their combinations. It makes it easier to work with complex data like images, media (audio/video). An object types is just an abstraction of the real world entities. An object has:
• Name
• Attributes
• Methods
Example:
Create type MyName as object (first varchar2(20), second varchar2(20));
Now you can use this datatype while defining a table below:
Create table Emp (empno number(5),Name MyName);
One can access the Atributes as Emp.Name.First and Emp.Name.Second
What is composite data type?
Composite data types are also known as Collections .i.e RECORD, TABLE, NESTED TABLE, VARRAY.
Composite data types are of 2 types:
PL/SQL RECORDS
PL/SQL Collections- Table, Varray, Nested Table
Differences between CHAR and NCHAR in Oracle
NCHAR allow storing of Unicode data in the database. One can store Unicode characters regardless of the setting of the database characterset
Differences between CHAR and VARCHAR2 in Oracle
CHAR is used to store fixed length character strings where as Varchar2 can store variable length character strings. However, for performance sake Char is quit faster than Varchar2.
If we have char name[10] and store “abcde”, then 5 bytes will be filled with null values, whereas in case of varchar2 name[10] 5 bytes will be used and other 5 bytes will be freed.
Differences between DATE and TIMESTAMP in Oracle
Date is used to store date and time values including month, day, year, century, hours, minutes and seconds. It fails to provide granularity and order of execution when finding difference between 2 instances (events) having a difference of less than a second between them.
TimeStamp datatype stores everything that Date stores and additionally stores fractional seconds.
Date: 16:05:14
Timestamp: 16:05:14:000
Define CLOB and NCLOB datatypes.
CLOB: Character large object. It is 4GB in length.
NCLOB: National Character large object. It is CLOB datatype for multiple character sets , upto 4GB in length.
What is the BFILE datatypes?
It refers to an external binary file and its size is limited by the operating system.
What is Varrays?
Varrays are one-dimensional, arrays. The maximum length is defined in the declaration itself. These can be only used when you know in advance about the maximum number of items to be stored.
For example: One person can have multiple phone numbers. If we are storing this data in the tables, then we can store multiple phone numbers corresponding to single Name. If we know the maximum number of phone numbers, then we can use Varrays, else we use nested tables.
What is a cursor? What are its types?
Cursor is used to access the access the result set present in the memory. This result set contains the records returned on execution of a query.
They are of 2 types:
1. Explicit
2. Implicit
New/User defined objects can be created from any database built in types or by their combinations. It makes it easier to work with complex data like images, media (audio/video). An object types is just an abstraction of the real world entities. An object has:
• Name
• Attributes
• Methods
Example:
Create type MyName as object (first varchar2(20), second varchar2(20));
Now you can use this datatype while defining a table below:
Create table Emp (empno number(5),Name MyName);
One can access the Atributes as Emp.Name.First and Emp.Name.Second
What is composite data type?
Composite data types are also known as Collections .i.e RECORD, TABLE, NESTED TABLE, VARRAY.
Composite data types are of 2 types:
PL/SQL RECORDS
PL/SQL Collections- Table, Varray, Nested Table
Differences between CHAR and NCHAR in Oracle
NCHAR allow storing of Unicode data in the database. One can store Unicode characters regardless of the setting of the database characterset
Differences between CHAR and VARCHAR2 in Oracle
CHAR is used to store fixed length character strings where as Varchar2 can store variable length character strings. However, for performance sake Char is quit faster than Varchar2.
If we have char name[10] and store “abcde”, then 5 bytes will be filled with null values, whereas in case of varchar2 name[10] 5 bytes will be used and other 5 bytes will be freed.
Differences between DATE and TIMESTAMP in Oracle
Date is used to store date and time values including month, day, year, century, hours, minutes and seconds. It fails to provide granularity and order of execution when finding difference between 2 instances (events) having a difference of less than a second between them.
TimeStamp datatype stores everything that Date stores and additionally stores fractional seconds.
Date: 16:05:14
Timestamp: 16:05:14:000
Define CLOB and NCLOB datatypes.
CLOB: Character large object. It is 4GB in length.
NCLOB: National Character large object. It is CLOB datatype for multiple character sets , upto 4GB in length.
What is the BFILE datatypes?
It refers to an external binary file and its size is limited by the operating system.
What is Varrays?
Varrays are one-dimensional, arrays. The maximum length is defined in the declaration itself. These can be only used when you know in advance about the maximum number of items to be stored.
For example: One person can have multiple phone numbers. If we are storing this data in the tables, then we can store multiple phone numbers corresponding to single Name. If we know the maximum number of phone numbers, then we can use Varrays, else we use nested tables.
What is a cursor? What are its types?
Cursor is used to access the access the result set present in the memory. This result set contains the records returned on execution of a query.
They are of 2 types:
1. Explicit
2. Implicit
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