In the Visual SQL Tuning (VST) diagram, a well-formed query would resemble the following:
Problems such as Cartesian joins, implied Cartesian joins, and many-to-many relationships are clearly represented in the VST.
Joins are represented with connecting lines between nodes. The following describes when a particular type of connecting line is used and the default positioning of the line.
| Connecting Lines | When Used |
|---|---|
| One-to-One Join relationships are graphed horizontally using blue lines. One-to-one joins exist when two tables are joined on their primary key. |
| One-to-Many Join relationships are graphed with the many table above the one table. |
| Cartesian Join shows the table highlighted in red with no connectors to indicate that it is joined in via a Cartesian join. The query is missing join criteria. A Cartesian join problem could be resolved by implementing a rewrite suggestion shown in the Generated Cases area of the Overview tab. |
| Many-to-Many Join relationships are connected by a red line and the relative location is not restricted. If master detail information is missing then the VST diagram will have many-to- many connectors. The optimizer can more consistently optimize a well-formed query, so the query will run faster. |
