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SQL Plus Interview Questions & Answers - Learning Mode
COOLINTERVIEW.COM ORACLE INTERVIEW QUESTIONS SQL PLUS INTERVIEW QUESTIONS QUESTIONS & ANSWERS - LEARNING MODE

SQL Plus Interview Questions & Answers - Learning Mode

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. SQL*Plus is essentially an interactive query tool with some scripting capabilities. You can enter a SQL statement, such as a SELECT query, and view the results.

Try SQL Plus Interview Questions & Answers - Exam Mode

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SQL Plus Interview Questions & Answers - Learning Mode
Try SQL Plus Interview Questions & Answers - Exam Mode
Question: How to get/select the nth row from the table ?
How to select first n rows ,last n rows from a table



Answer: nth salary

select salary

from table_name a

where &n=(select count(salary) from table_name b where a.salary<=b.salary);

n salaries

select salary

from table_name a

where &n>=(select count(salary) from table_name b where a.salary<=b.salary);
Source: CoolInterview.com
Question: What is meant by Scrollable cursor

Answer: A scrollable cursor, however, can move forward and backward, and can seek any desired record in the cursor. Such operations are common in applications that present results sets in scrolling windows. With a scrollable cursor, application developers do not need to create and manage their own buffer for the records. Source: CoolInterview.com
Question: Subquery vs Join

Answer: subquery retrive the data depending on certain condition or manupulation in inner query.

where as joins will join the enitire data depending on the conditions given it cannot manupulate the data or we cannot be selective while using joins


Source: CoolInterview.com
Question: Find out nth highest salary from emp table

Answer: select sal from emp E
wherenulln-1=(select count( distinct sal) from emp where
sal>E.sal); Source: CoolInterview.com
Question: Display the records between two range I know the nvl function only allows the same data type(ie. number or char or date Nvl(comm, 0)), if commission is null then the text ?Not Applicable? want to display, instead of blank space. How do I write the query

Answer: You can use the decode function for the above requirement. Please find the query as below:

select ename,decode(nvl(comm,0),0,'Not Applicable',comm) from scott.emp;

Source: CoolInterview.com
Question: Explain CONNECT BY PRIOR

Answer: Retrieves rows in hierarchical order.e.g. select empno, ename from emp where.
Source: CoolInterview.com
Question: What is the maximum number of triggers, can apply to a single table

Answer: Insert/Update/Delete :- 3
Before/After:- 2
Row Level/Statement Level:-2

Hence 3*2*2 Source: CoolInterview.com
Question: What is difference between CHAR and VARCHAR2?

Answer: CHAR pads blank spaces to the maximum length. VARCHAR2 does not pad blank spaces. For CHAR it is 255 and 2000 for VARCHAR2. Source: CoolInterview.com
Question: Can a view be updated/inserted/deleted? If Yes under what conditions ?

Answer: A View can be updated/deleted/inserted if it has only one base table if the view is based on columns from one or more tables then insert, update and delete is not possible. Source: CoolInterview.com
Question: If an unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE ?

Answer: It won't, Because SYSDATE format contains time attached with it. Source: CoolInterview.com
Question: What are PL/SQL Cursor Exceptions

Answer: Cursor_already_open, Invalid_cursor

Source: CoolInterview.com
Question: Explain the different types of joins

Answer: Join is a query which retrieves related columns or rows from multiple tables.Self Join - Joining the table with itself.Equi Join - Joining two tables by equating two common columns.Non-Equi Join - Joining two tables by equating two common columns.Outer Join - Joining two tables in such a way that query can also retrieve rows that do not have corresponding join value in the other table. Source: CoolInterview.com
Question: What are the pre-requisites to modify datatype of a column and to add a column with NOT NULL constraint

Answer: 1) to modify datatype of a column - ???
2) to add a column with NOT NULL constraint - the table must have 0 rows Source: CoolInterview.com
Question: What are the usage of SAVEPOINTS ?

Answer: SAVEPOINTS are used to subdivide a transaction into smaller parts. It enables rolling back part of a transaction. Maximum of five save points are allowed. Source: CoolInterview.com
Question: Explain UNION, MINUS, UNION ALL and INTERSECT

Answer: INTERSECT returns all distinct rows selected by both queries.MINUS - returns all distinct rows selected by the first query but not by the second.UNION - returns all distinct rows selected by either queryUNION ALL - returns all rows selected by either query, including all duplicates. Source: CoolInterview.com
Question: How do I eliminate the duplicate rows?

Answer: Use the DISTINCT keyword right after SELECT...

i.e. SELECT DISTINCT customername FROM customer Source: CoolInterview.com
Question: How many LONG columns are allowed in a table ? Is it possible to use LONG columns in WHERE clause or ORDER BY ?

Answer: Only one LONG columns is allowed. It is not possible to use LONG column in WHERE or ORDER BY clause. Source: CoolInterview.com
Question: How can you call a PL/SQL procedure from SQL?

Answer: By use of the EXECUTE (short form EXEC) command. Source: CoolInterview.com
Question: What is a Non- corelated subquery

Answer: Non corelated subquery, where the subquery has been executed once for the entire parent statement. Source: CoolInterview.com
Question: You want to determine the location of identical rows in a table before attempting to place a unique index on the table, how can this be done?

Answer: Oracle tables always have one guaranteed unique column, the rowid column. If you use a min/max function against your rowid and then select against the proposed primary key you can squeeze out the rowids of the duplicate rows pretty quick. For example:
select rowid from emp e
where e.rowid > (select min(x.rowid)
from emp x
where x.emp_no = e.emp_no);
In the situation where multiple columns make up the proposed key, they must all be used in the where clause. Source: CoolInterview.com

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