One of my colleagues came to me with this statement:

> 
> Having a `SELECT` on a table that fetch 80% of the rows while having a
>  `WHERE` clause on a column with an index. So to avoid that add a `WITH (NOLOCK)` in your `FROM` clause.
> 
> 
> 

His only argument was: *Believe me I've experienced it myself.* I cannot find a proper documentation for this.

I far has I know `WITH (NOLOCK)` only affects the table by letting `UPDATE` and `INSERT` occur while selecting and that can lead us to dirty read.

Is my colleague's assumption correct?