There are two phrases for selecting records: WHERE and IF. It is recommended that you use WHERE to select records. IF offers a subset of the functionality of WHERE. Everything that you can accomplish with IF, you can also accomplish with WHERE. WHERE can accomplish things that IF cannot.
If you used IF to select records in the past, remember that WHERE and IF are two different phrases, and may require different syntax to achieve the same result.
WHERE syntax is described and illustrated throughout this topic. For details on IF syntax, see Selecting Records Using IF Phrases.