First off Im not a dba and Im fairly new to sql. These questions are probably basic SQL knowledge but here are the questions:

1. Say there are 75 million records in the database with about 100 columns. If you run a simple SELECT query with a couple where clauses, could this cause the system to "slow down" or "bog the system down"? I know hardware and usage play a part but lets just say thats not a concern.

2. How does the SELECT statement with where clauses search the database? Does it first look at the where clauses? For example: WHERE phone_number = 555555555. Does it go to the phone_number column and search ALL the phone numbers?

3. If there a more than one where clause, which where clause is processed first or are they processed simultaneously?

4. Is there a better way to search the db so these queries do not impact server performance?

Thanks for the help.

for all your issues ,you need ot create indexes in column that is frequently bsing using in where clause of queries.