The name of relation is the easiest query in relational algebra. The name of relation query results are just the whole relation as well.This type of algebra is a formal language, and can be seen to have been used to form languages such as SQl. Although relational algebra can be used to form SQL, a common difference found between SQL and relational algebra is that SQL uses multi sets, meaning that duplicate values are not removed. Also, relational algebra lacks 2 rows with the same values. This is because duplicate values are always removed from these columns. To look at a subset of columns and rows a project operator using the select operator is needed to see a small amount of both. To only use a part of the columns a pi symbol is needed.
The command select requires a sigma to be used in order to pick out certain rows from the original relation. When doing this, only a subset of the relation is then returned. Next, to base this new subset odd two different conditions a caret is then used. Monday we learned how a Cartesian product combines two relations. This needs natural join and this is necessary when selecting information from various amounts of tables that meet decided conditions. Now, if using database management systems a join called the theta join is needed, which adds a theta condition that has to be then passed.
Now some key ideas/definitions would be that the rename operator is needed to join two relations. This means that it has to reassign the schema.Next, to return rows that are identical in two other relations an intersection operator is then used. Additionally, to remove values that are present in another relation we need to combine information by adding rows to the table. A union operator is then needed to do so.