Speed of query, based on number of conditions?

Question

I have a table. specs[id,name,store_id,section_id,category_id,user_id,model_id]
My query is very simple:

SELECT * FROM specs
WHERE
    store_id=1
    AND
    section_id=1
    AND
    category_id=1
    AND
    user_id=1
    AND
    model_id=1

What I receive in result, is a list of specs.
If I will change the query to:

SELECT * FROM specs WHERE model_id=1

I will get the SAME results, since the table can have duplicates (excluding the id, of-course)
Data sample (note that :

  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

The DB is MySQL.

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?

edit

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.
So it doesn't really matter what other conditions are supplied, since the model is the key.

Answer 1

1. The result of the two query will not necessary be the same. More conditions might have less rows as a result.
2. As a general rule, you cannot say more conditions will make it faster. Under certain circumstances it is possible but not probable. It all depends on what kind of indexes you define on the table.

Here's one of my older answer on multi-column where clauses and indexes in MySQL.