Below are some important Oracle Database interview questions which are asked in most MNC company interviews for beginners or professionals.
11. What Is a User Role in Oracle?
A user role is a group of privileges. Privileges are assigned to users through user roles. You create new roles, grant privileges to the roles, and then grant roles to users.
12. What is a Database Schema in Oracle?
A schema is a collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user. Each user owns a single schema. Schema objects can be created and manipulated with SQL and include: tables, views, and other types of data objects.
13. What Is a Database Table in Oracle?
A database table is a basic unit of data logical storage in an Oracle database. Data is stored in rows and columns. You define a table with a table name, such as employees, and a set of columns. You give each column a column name, such as employee_id, last_name, and job_id; a datatype, such as VARCHAR2, DATE, or NUMBER; and a width. The width can be predetermined by the datatype, as in DATE. If columns are of the NUMBER datatype, define precision and scale instead of width. A row is a collection of column information corresponding to a single record.
14. What Is a Table Index in Oracle?
Index is an optional structure associated with a table that allow SQL statements to execute more quickly against a table. Just as the index in this manual helps you locate information faster than if there were no index, an Oracle Database index provides a faster access path to table data. You can use indexes without rewriting any queries. Your results are the same, but you see them more quickly.
15. What Is an Oracle Tablespace?
An Oracle tablespace is a big unit of logical storage in an Oracle database. It is managed and used by the Oracle server to store structures data objects, like tables and indexes.
16. What Is an Oracle Data File?
An Oracle data file is a big unit of physical storage in the OS file system. One or many Oracle data files are organized together to provide physical storage to a single Oracle tablespace.
17. What Is a Static Data Dictionary in Oracle?
Data dictionary tables are not directly accessible, but you can access information in them through data dictionary views. To list the data dictionary views available to you, query the view DICTIONARY. Many data dictionary tables have three corresponding views:
* An ALL_ view displays all the information accessible to the current user, including information from the current user's schema as well as information from objects in other schemas, if the current user has access to those objects by way of grants of privileges or roles.
* A DBA_ view displays all relevant information in the entire database. DBA_ views are intended only for administrators. They can be accessed only by users with the SELECT ANY TABLE privilege. This privilege is assigned to the DBA role when the system is initially installed.
* A USER_ view displays all the information from the schema of the current user. No special privileges are required to query these views.
18. What Is a Dynamic Performance View in Oracle?
Oracle contains a set of underlying views that are maintained by the database server and accessible to the database administrator user SYS. These views are called dynamic performance views because they are continuously updated while a database is open and in use, and their contents relate primarily to performance. Although these views appear to be regular database tables, they are not. These views provide data on internal disk structures and memory structures. You can select from these views, but you can never update or alter them.
19. What Is a Recycle Bin in Oracle?
Recycle bin is a logical storage to hold the tables that have been dropped from the database, in case it was dropped in error. Tables in recycle bin can be recovered back into database by the Flashback Drop action. Oracle database recycle save the same purpose as the recycle bin on your Windows desktop.
Recycle bin can be turned on or off in the recyclebin=on/off in your parameter file.
20. What Is SQL*Plus?
SQL*Plus is an interactive and batch query tool that is installed with every Oracle Database Server or Client installation. It has a command-line user interface, a Windows Graphical User Interface (GUI) and the iSQL*Plus web-based user interface.
11. What Is a User Role in Oracle?
A user role is a group of privileges. Privileges are assigned to users through user roles. You create new roles, grant privileges to the roles, and then grant roles to users.
12. What is a Database Schema in Oracle?
A schema is a collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user. Each user owns a single schema. Schema objects can be created and manipulated with SQL and include: tables, views, and other types of data objects.
13. What Is a Database Table in Oracle?
A database table is a basic unit of data logical storage in an Oracle database. Data is stored in rows and columns. You define a table with a table name, such as employees, and a set of columns. You give each column a column name, such as employee_id, last_name, and job_id; a datatype, such as VARCHAR2, DATE, or NUMBER; and a width. The width can be predetermined by the datatype, as in DATE. If columns are of the NUMBER datatype, define precision and scale instead of width. A row is a collection of column information corresponding to a single record.
14. What Is a Table Index in Oracle?
Index is an optional structure associated with a table that allow SQL statements to execute more quickly against a table. Just as the index in this manual helps you locate information faster than if there were no index, an Oracle Database index provides a faster access path to table data. You can use indexes without rewriting any queries. Your results are the same, but you see them more quickly.
15. What Is an Oracle Tablespace?
An Oracle tablespace is a big unit of logical storage in an Oracle database. It is managed and used by the Oracle server to store structures data objects, like tables and indexes.
16. What Is an Oracle Data File?
An Oracle data file is a big unit of physical storage in the OS file system. One or many Oracle data files are organized together to provide physical storage to a single Oracle tablespace.
17. What Is a Static Data Dictionary in Oracle?
Data dictionary tables are not directly accessible, but you can access information in them through data dictionary views. To list the data dictionary views available to you, query the view DICTIONARY. Many data dictionary tables have three corresponding views:
* An ALL_ view displays all the information accessible to the current user, including information from the current user's schema as well as information from objects in other schemas, if the current user has access to those objects by way of grants of privileges or roles.
* A DBA_ view displays all relevant information in the entire database. DBA_ views are intended only for administrators. They can be accessed only by users with the SELECT ANY TABLE privilege. This privilege is assigned to the DBA role when the system is initially installed.
* A USER_ view displays all the information from the schema of the current user. No special privileges are required to query these views.
18. What Is a Dynamic Performance View in Oracle?
Oracle contains a set of underlying views that are maintained by the database server and accessible to the database administrator user SYS. These views are called dynamic performance views because they are continuously updated while a database is open and in use, and their contents relate primarily to performance. Although these views appear to be regular database tables, they are not. These views provide data on internal disk structures and memory structures. You can select from these views, but you can never update or alter them.
19. What Is a Recycle Bin in Oracle?
Recycle bin is a logical storage to hold the tables that have been dropped from the database, in case it was dropped in error. Tables in recycle bin can be recovered back into database by the Flashback Drop action. Oracle database recycle save the same purpose as the recycle bin on your Windows desktop.
Recycle bin can be turned on or off in the recyclebin=on/off in your parameter file.
20. What Is SQL*Plus?
SQL*Plus is an interactive and batch query tool that is installed with every Oracle Database Server or Client installation. It has a command-line user interface, a Windows Graphical User Interface (GUI) and the iSQL*Plus web-based user interface.
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