The following schema appears in Chris Date's book An introduction to Database Systems. There are three relvars in the schema, used to represent suppliers, parts and shipments. It is a conventional normalised relational database schema.
Predicate: There exists a supplier identified by supplier number [S#] with name [SNAME] having status [STATUS] and located in city [CITY]
| S# | SNAME | STATUS | CITY |
|---|---|---|---|
| S1 | Smith | 20 | London |
| S2 | Jones | 10 | Paris |
| S3 | Blake | 30 | Paris |
| S4 | Clark | 20 | London |
| S5 | Adams | 30 | Athens |
Predicate: There exists a kind of part identified by part number [P#] with name [PNAME] having colour [COLOR], weight [WEIGHT] and which are stored in city [CITY].
| P# | PNAME | COLOR | WEIGHT | CITY |
|---|---|---|---|---|
| P1 | Nut | Red | 12.0 | London |
| P2 | Bolt | Green | 17.0 | Paris |
| P3 | Screw | Blue | 17.0 | Oslo |
| P4 | Screw | Red | 14.0 | London |
| P5 | Cam | Blue | 12.0 | Paris |
| P6 | Cog | Red | 19.0 | London |
Predicate: There exists a supplier identified by supplier number [S#] that ships quantity [QTY] of a part identified by part number [P#].
| S# | P# | QTY |
|---|---|---|
| S1 | P1 | 300 |
| S1 | P2 | 200 |
| S1 | P3 | 400 |
| S1 | P4 | 200 |
| S1 | P5 | 100 |
| S1 | P6 | 100 |
| S2 | P1 | 300 |
| S2 | P2 | 400 |
| S3 | P2 | 200 |
| S4 | P2 | 200 |
| S4 | P4 | 300 |
| S4 | P5 | 400 |