The importance of Relational Algebra
- So far we have considered how to structure data using the relational model.
- We need a language to answer questions — queries — about the data.
- SQL is that language.
- Before we get to SQL, it is important to learn Relational Algebra.
- is the basis of SQL semantics,
- And of query optimization techniques which are essential to making SQL practical.
Relational Algebra
- A set-at-a-time language was a revolutionary idea in 1970,
because all database languages at the time were record-at-a-time.