# Database concepts

Let's define a few concepts

<div class="Lesson_content__j6FUx" id="bkmrk-rows-are-referred-to">- rows are referred to as **records**
- columns are referred to as **fields**

</div>The number of records in a database is unlimited, but the number of fields is limited to the number of fields that were created for the table. Field naming is important because we use it when writing SQL queries. Field names should be lowercase, without spaces, and singular because the field refers to a single record. For example:

<div class="Lesson_content__j6FUx" id="bkmrk-full_name-instead-of">- full\_name instead of FullNames
- firstname instead of firstName
- salary instead of salaries

</div>It is not allowed to name two different fields with the same name, as this can lead to confusion and difficulty in distinguishing between a table name and a field. To identify different records, it is best to use a unique identifier called a "key". Every table should have a key field, as it allows us to distinguish between two similar records. This key field is usually referred to as the "id".