i want to count of no. of rows from multiple tables and create one output table and load data with curent datetime column and another one column of "total time of job running". ? which component or which expression i used? help
Look at the components you are using by making use of Talend's component guides (https://help.talend.com/search/all?query=Talend+Components+Reference+Guide). For each component there is a Global Variables section which describes variables that Talend assigns values to informing you of certain component metrics. You can see these in the "Outline" window in the bottom left of the Studio. Expand the tree for your component and you can see the Global Variables available and also drag them to a tJava (or other components) so that you can make use of them. They are stored in a Java HashMap called "globalMap.
This tutorial shows it in more detail https://www.talendbyexample.com/talend-studio-outline-panel-reference.html
I'm afraid the best way to learn Talend (anything) is to try it out. Have a play and see what you can figure out based on what I have told you and the links I've supplied.