# Relational Operators

There are 8 relational operators:

1. **SELECT**  \
   Selects rows from a table that have specified attribute values.
2. **PROJECT**  \
   Selects rows made up of a subset of columns from a table.
3. **JOIN**  \
   Associates entries from two tables on the basis of matching column values.\
   ![](https://1736932896-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M5-0RGXrGEYT2sPemdS%2F-M5-0Rgnjb23s9oFr3lT%2F-M5-0_QjVze3qn3fNAgc%2FJOINS.png?generation=1586990836043770\&alt=media)
4. **PRODUCT**  \
   Builds a relation from two specified relations consisting of all possible combinations of rows, one from each of the two relations.
5. **UNION**  \
   Builds a relation consisting of all rows appearing in either or both of the two relations.
6. **INTERSECT**  \
   Builds a relation consisting of all rows appearing in both of the two relations.
7. **DIFFERENCE**  \
   Builds a relation consisting of all rows appearing in the first and not in the second of the two relations.
8. **DIVIDE**  \
   Takes two relations, one binary and one unary, and builds a relation consisting of all values of one column of the binary relation that match, in the other column, all values in the unary relation.\
   Ex.\
   **A: B:**  \
   a x x

   a y y

   a z

   b x

   c y

   \=> **A DIVIDE B**: a\
   Basically, A/B = \<m> such that for every n value in a tuple of B there is \<m, n> in A.