How to modify SQL in best way is I have given in this post two options. You can choose appropriately.
The best 1000 SQL queries to practice daily. Read more.
The best way to understand IF coding in SQL stored procedure and in COBOL with simplified examples really good for quick refresh.
The best example for TRUNC function that truncates to nearest date format in SQL
The GROPU BY clause is very much interesting and it is being used in many sql development project. The summary and key points given here like that you never forgotten about what is Group BY in sql. The SQL is well explained with an example. Read more.
The Associate cursor in DB2 is being used in Stored procedure. The purpose is while calling a Stored procedure from an another stored procedure this Associate acts as to hold result set.
Without Views there is no program in any project. Since there are lot of benefits with Views. Many programmers still have confusion how to create Views and why Views are required. This post clears all your questions with syntax for Views in SQL.
There are four different SQL functions in SQL. Each function makes you so confuse when you are very beginner. This post explains SQL functions in Simple manner for beginners as well as for advanced programmers and developers.
The secondary index is most critical object, after the primary index. This post explains the most optimum value for number of secondary indexes you can give on any Table.
The best and mostly asked SQL query is converting rows into columns. This is a tricky question and it needs little intelligence to write effectively. This SQL query can be written in two steps with SQL functions either CASE or DECODE.