The way is to ask better questions.
Firstly, I've edited your tags list and removed all tags but SQL Server, since they had no relation whatsoever to your question. Please, be more considerate in the future when you post questions.
Next, just dumping an image without telling us what you want to achieve is not a good way to ask a question. A better approach is to say "I have this table" and post the CREATE TABLE statement for the table, "and I have this data" and post INSERT statements with the sample data, and then say "these are my business rules and I want this result". The result you can post as an image, but the tables and sample data should be as text so that we can copy into a query window to develop a tested solution.
Now, let's look at the image you post. First you run two SELECT against two different tables. They have similar names, but they are different nonetheless. Next, you update all rows in S_Student to replace 'a' with 'xxxx'. In the final query you look for rows in that very table that start with the letter you just replaced. And you are asking why you don't any rows back?