When Only Enter On Search Buuton Then No Result Find

I have created a search page which has a text field and button to search.When searching, if you dont enter anything into the text field, you get no results. I would prefer that everything in the database shows rather than nothing. I am told that if you enter '%' into the text field everything will come up. But how would I make this happen automaticaly rather than the person searching typing this in every time?

Text field code:
<input name="keywordSearch" type="text" id="keywordSearch">

Button code:
<input name="Search" type="submit" id="Search" value="Search">