Thanks all for your fine comments. I do use WHERE and LIMIT as appropriate. LIMIT 1 is my most common, since each DB item is unique in most tables. For employment histories (in another table) there can be many entries with similar identifiers, but I set LIMIT 25 since it is unlikely anyone has 25 prior employment histories.
In some cases, where a search is used, SELECT * FROM with no limits is used but WHERE clauses are used.
And, Roger, technically I am an amateur when it comes to PHP. I've got about 16 months experience writing in PHP and I still don't know everything I should. Anywhere I can improve is great for me and my customers/hosts.
Brad: Most queries require ALL of the columns in a particular row, but not all the rows. These are employment applications and no data can be left out when the data is retrieved, so nearly every single column is used. I've got one table with over 300 columns that stores skill data for each applicant. LIMIT 1 still applies here, which theoretically should stop the search process once the unique row is located.
Thanks again, folks, for your insightful remarks!