title: Speed of query, based on number of conditions?
body: <p>I have a table. <code>specs[id,name,store_id,section_id,category_id,user_id,model_id]</code><br>
  My query is very simple:  </p>
  
  <pre><code>SELECT * FROM specs
  WHERE
      store_id=1
      AND
      section_id=1
      AND
      category_id=1
      AND
      user_id=1
      AND
      model_id=1
  </code></pre>
  
  <p>What I receive in result, is a list of specs.<br>
  If I will change the query to:</p>
  
  <pre><code>SELECT * FROM specs WHERE model_id=1
  </code></pre>
  
  <p>I will get the SAME results, since the table can have duplicates (excluding the <code>id</code>, of-course)<br>
  Data sample (note that :</p>
  
  <pre><code>  id  |  name  |  model_id  |  section_id  |category_id  |  user_id
    ------------------------------------------------------------------
    1   | me     | 22         | 5            |   11        |   777
    2   | you    | 22         | 5            |   11        |   777
    3   | me     | 22         | 5            |   11        |   777
    4   | me     | 22         | 5            |   11        |   777
    5   | you    | 33         | 5            |   11        |   777
    6   | they   | 33         | 5            |   11        |   777
    7   | them   | 33         | 5            |   11        |   777
    8   | we     | 33         | 5            |   11        |   777
    9   | we     | 33         | 5            |   11        |   777
    10  | them   | 44         | 5            |   11        |   776
    11  | they   | 44         | 5            |   11        |   776
    12  | me     | 44         | 5            |   11        |   776
    13  | you    | 44         | 5            |   11        |   776
    14  | they   | 44         | 5            |   11        |   776
    15  | them   | 44         | 5            |   11        |   776
  </code></pre>
  
  <p>The DB is MySQL.</p>
  
  <p>The question: since the table will contain 500k-1000k records, would it be faster to use the first query or the second? more conditions will make it faster? slower?</p>
  
  <h2>edit</h2>
  
  <p>When a record is being added, the user must supply a value for ALL columns. and the records are ALWAYS attached to a model_id.<br>
  So it doesn't really matter what other conditions are supplied, since the model is the key.</p>