Science and mathematics. STEM can also be engineering but in John’s case, he’s a METEOROLOGIST WHO DOES THE WEATHER FORECAST and meteorologists is part of a study in science and also mathematics because of measuring the speed of some related computations
Thus is true
Encryption helps to keep data virtually safe
A composite primary key<span> is a set of several primary </span>keys<span> that, together, uniquely identifies each record.</span>
Primary keys are used as identifiers of composite entities. In this case each primary key combination is allowed only once in the *:* relationship.
Other case where primary keys are used is as identifiers of weak entities, where the weak entity has a strong identifying relationship with the parent entity.
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