Converting Rows to Single Column

Strange solution for someone who is looking into this statement for the first time.

I have used XMLAGG, XMLELEMENT and EXTRACT functions. See if you can crack it.

XMLAGG is an aggregate/group function which aggregates all the values for a column.
XMLELEMENT is a function which creates XML tags with tag element E.
EXTRACT function then removes all the XML text and retains only text.

SELECT deptno, XMLAGG (XMLELEMENT (e, ename || ',')).EXTRACT ('//text()') as ENAMES
FROM
emp
GROUP BY deptno;

This statement will give you an output as below,

If you observe in this output, there is an extra comma at the end of the ENAMEs list. To remove this, I shall use another function RTRIM which is used to trim characters on the right side.

SELECT deptno, RTRIM(XMLAGG (XMLELEMENT (e, ename || ',')).EXTRACT ('//text()'),',') as ENAMES
FROM
emp
GROUP BY deptno;

In case if the output does not show the values properly then use the following command to restrict the column length.

COLUMN ENAMES FORMAT A50

Happy Learning!!!!!!!

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SQL Interview Questions on Subqueries

SUB Queries:
1. List the employees working in research department 2. List employees who are located in New York and Chicago
3. Display the department name in which ANALYSTS are working
4. Display employees who are reporting to JONES
5. Display all the employees who are reporting to Jones Manager
6. Display all the managers in SALES and ACCOUNTING department
7. Display all the employee names in Research and Sales Department who are having at least 1 person reporting to them
8. Display all employees who do not have any reportees
9. List employees who are having at least 2 reporting
10. List the department names which are having more than 5 employees
11. List department name having at-least 3 salesman
12. List employees from research and accounting having at-least 2 reporting
13. Display second max salary
14. Display 4th max salary
15. Display 5th max salary -- Answer for nth Max Salary
Co-Related Subqueries:
16. Write a query to get 4th max salary from EMP table
17. Write a query to get 2nd…

Basics of RDBMS

Data
Small set of information becomes data, this set of information helps make decision. Data is always some useful information.

Database
Place where you store the data. Database represents some aspect of the real world called "miniworld". A database is designed, built and populated with data for a specific purpose. It has intended group of users and some preconceived applications in which these users are interested.

In other words, a database has some source from which data is derived, some degree of interaction with events in the real world and an audience that is actively interested in the contents of the database.

Database can also be defined as collection of one or more tables.

Ex: Mobile, human brain etc

DBMS (Database Management System)
Is a program that stores retrieves and modifies data in the database on request.

Study of different techniques of design, development and maintenance of the database

Types of DBMS
These types are based upon their management of database s…

Answers for SQL Functions

1. SQL> SELECT empno, ename FROM emp WHERE Length(ename) = 4;

2. SQL> SELECT empno, ename, job FROM emp where Length(job)=7;

3. SQL> SELECT Length('qspiders') - Length(replace('qspiders','s','')) FROM dual;

4. SQL> SELECT empno, ename, job FROM emp WHERE Instr(job,'MAN') >0;

5. SQL> SELECT empno, ename, job FROM emp WHERE Instr(job, 'MAN') =1;

6. SQL> SELECT empno, ename, job FROM emp WHERE (Length(ename) - Length(Replace(ename, 'L',''))) = 1;

7. SQL> SELECT * FROM dept WHERE Instr(dname,'O') > 0;

8. SQL> SELECT Concat(ename,' working as a ') || Concat(job, ' earns ') || Concat(sal, ' in ') || Conc
at('dept ',deptno) AS text from emp;

OR

SQL> SELECT Concat(Concat(Concat(Concat(Concat(Concat(Concat(ename,' working as a '), job),' earns '), sal),' in '),'dept '), deptno) AS text FROM emp;

9. SQL> SELECT empno, ename…

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