Read balakuruswamy c, c++,java .
Ssi material for unix .
For oracle, sql commands from any book.and dbms concepts.

From c
" Pointer
" Dynamic memory allocation
" Printf and scanf stmt
" Structure
" Array

From c++
" Function overloading and over riding
" Virtual fn
" Inheritance
" Basic oops concepts
" Inline fn
" Exception handling[ try, catch throw -->enough]
From java
" Thread
" Inheritance
" Super fn and keyword
" Constructor
" Garbbage collection
" Operators and data type.

From oracle
" Std sql cmds
" Std dbms concepts[ normalization, constraints]

From unix
" Basic unix cmds
" Std os concepts[ thread, deadlock, process handling, scheduling algorithm