A key is a piece of metal that fits into a lock, turns, and opens it. Many people keep keys on their key ring, but some use plastic ones. Without a key, your attendance is worthless. Other meanings of the word key include button, lever, explanation, or correct pitch. Read on to learn how to make one. Listed below are several examples of different keys and their uses. Let’s start with the most common.
The tonic is the most important note in any song. It acts like the center of gravity. When we think of gravity, all objects gravitate towards the Earth’s center, which is the tonic. The tonic is also known as the center of a key, which means that it is the most resolved note in the scale. You can also consider the tonic as the “humming” note of the piece of music. In terms of music, the tonic is the note on which all other notes of the piece are based.
In a database, the key is a field or a combination of fields in a table. It serves as the link between two tables and helps to retrieve data faster. In relational databases, keys are often used as foreign and primary. Primary keys enforce entity integrity by holding unique values, while foreign keys help maintain referential integrity. If a table contains multiple rows with duplicate records, a key will enforce the integrity of the relationship. The key may be a single attribute, or a set of attributes that are associated with an individual row.