Sharing Knowledge by Mithun Ashok

Displaying alternate rows of EMP table,

The Year 1970.....

This was one of the fabulous years in the history of Computers when one of the best inventions of Computers took place,

1. RDBMS by EF Codd
2. C by Dennis Ritchie

C was first implemented by Dennis Ritchie on a DEC PDP-11 running on Unix OS. C was the result of an older Language BCPL developed by Martin Richards and later took a transformation and led to the birth of language B by Ken Thompson inturn leading to development of C by Dennis.

The first book on C was released by Prentice-Hall in 1978 by Kernighan and Dennis Ritchie with the name The C Programming Language.

C was finally standardized in December 1989 when ANSI adopted the standard for C and was know as programmers language designed by and for programmers.

This transformation in the field of Programing languages started with language BASIC, COBOL and then to FORTRAN and to more structured programming language PASCAL.

All this transformation led to the creation of C++ which is a direct descendent of C and then C+…

One of my students asked me this question of swapping of first rows ename with last rows ename.
This is very simple if you know CASE conditional expression.
Check the select statement below,

SELECT x.ename, x.sal, y.ename, y.sal, x.sal - y.sal 
FROM (select ename,sal,rownum a from emp) x, (select ename, sal, rownum b from emp) y
WHERE x.a+1 = y.b;