title: Database model for storing expressions and their occurrence in text
body: <p>I'm doing a statistical research application. I need to store words according to 2 initial letters which is 676 combinations and each word has its number of occurrences (minimal, maximal, average) in text. I'm not sure how the model/schema should look like. There will be a lot of checking whether the keyword was already persisted. I appreciate your suggestions.  </p>
  
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  <p>Edit: I'll be using either mysql or postgresql + spring templates</p>