Here is the scenario: lets say I have a database named
sqlprac that contains a table named
There are two ways to write a query:
use sqlprac /*1*/ SELECT dept.deptno, dept.deptname, dept.deptsal FROM dept; /*2*/ SELECT deptno, deptname, deptsal FROM dept;
Both queries should return the same result set. However I have seen that this isn't always the case, especially in sub query/inner query. What's the difference then?
Why should I choose one over another?
Also, a third query might be
/*3*/ SELECT * FROM dept
I know what
* is doing, but in which case we should or not use it.
Are there any performance/optimization issues?