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Introduction
A powerful way to study database data is to navigate between the tables
in a schema by following table relationships declared by primary and
foreign keys. DbVisualizer includes a Navigator feature for this
purpose, visualizing the relationships graphically while making the
data for each navigation case easily accessible in a data grid.
To launch the Navigator,
select
the table you want to start the navigation from in the Database Objects
Tree, and then open the Navigator tab in the Object View.
Figure: The
Navigator tab showing the initial table
The Navigator has two parts: a graphical view and a data grid.
Initially, the graphical view shows just the selected start
table,
and the data grid shows the data for the start table.
The data grid is a read-only grid of the same type as you encounter in
other parts of DbVisualizer, but extended with a Related Table list and
a Tag button. You can learn more about the general data grid in the Data
Grid section of the Getting Started
chapter. The Navigator specific extensions are described in detail in
the following section.
Data
Navigation
Data navigation in DbVisualizer means following table relationships
declared by primary and foreign keys, using a unique key value. In the
example schema shown in the screenshots in this section, there is a
table named DEPARTMENTS with a primary key named DEPARTMENT_ID. Another
table named EMPLOYEES has a foreign key constraint, declaring that
values in its DEPARTMENT_ID column refer to primary key values in the
column with the same name in the DEPARTMENTS table.
Figure: The
Related Table list
If you use DEPARTMENTS as you start table, you can easily navigate to
the EMPLOYEES table for different DEPARTMENT_ID values. In the data
grid, select one or more columns in the row that holds the
DEPARTMENT_ID you want to use for navigation. In the figure above, the
DEPARTMENT_NAME column in the row for DEPARTMENT_ID = 60 is selected.
Next, bring up the Related Table list. It lists all tables the
DEPARTMENTS table is related to through primary and foreign keys, with
the key columns within parenthesis. A forward arrow (->) in
front of
the table name means that the DEPARTMENTS table has a foreign key
relation to the named table. A backward arrow (<-) means that
the
named table has a foreign key relation to the DEPARTMENTS table.
Figure: Tooltip
for a Related Table list entry
The Related Table list shows only the table name and
columns of the related table, because there is not room for more when a
key contains many columns with long names. Sometimes this information
is not enough to
understand what the relation really means. To make it easier to figure
out,
you can let the mouse hover over a list entry. A tooltip then shows you
the other end of the relation as well, e.g., in the figure above, the
tooltip shows that "<- EMPLOYEES (DEPARTMENT_ID)" represents a
foreign key from the EMPLOYEES DEPARTMENT_ID column to the DEPARTMENTS
DEPARTMENT_ID column.
Figure:
Navigation from DEPARTMENTS to EMPLOYEES for DEPARTMENT_ID = 60
When you select "<- EMPLOYEES (DEPARTMENT_ID)" in the
Related
Table list, a node is added to the graph for the EMPLOYEES table, with
an arrow from the DEPARTMENTS table node to show the navigation
direction. We call this a navigation case.
The EMPLOYEES node contains the key columns (just one in this example)
and their values.
The arrow betwwen the nodes is labeled with the key column name. In
addition, the arrow label also shows the name and value of the column
that you selected in the DEPARTMENTS table when you created this
navigation case, i.e., the DEPARTMENT_NAME column. If you select
multiple columns when you create a navigation case, all non-key column
names and values are included in the arrow label. This can make it
easer to see at a glance what a navigation case represents.
The grid is also updated when you create a navigation case, to show all
rows in the table you navigated to that has a key value corresponding
to the selected key value in the table you navigated from. In this
case, it shows all rows in the EMPLOYEES table with DEPARTMENT_ID equal
to 60.
You can continue to create more navigation cases from any node
in
the graph. For instance, if the schema contains a table with job
history for employees, you can navigate to the history for an employee
from the EMPLOYEES node. Or, you can select the DEPARTMENTS node in the
graph to navigate to the EMPLOYEES table for a different department.
Just click on the DEPARTMENTS node, select another row in the data grid
and then the same Related Table list entry.
Figure: Two
navigation cases
Every time you select a node in the graph, the data grid is updated to
show the corresponding data. The grid settings for one node are
independent of the settings for another node. For instance, if
you
define a filter for one node, the filter is only associated with the
grid for that node.
Adding
Context Information to the Graph
The navigation node always show the key columns and their values, but
sometimes you may want to add other columns to the node to better
describe what it represents. This is called tagging the node.
There are two ways to do so: drag and drop cells from the grid to any
node, or use the Tag
button in the grid toolbar to tag the currently selected node
with the currently selected cells in the grid.
To drag and drop cells to a node, select one or more cells in the grid.
With the left mouse button pressed and the mouse positioned over one of
the selected cells, drag the cells over a node in the graph and release
the mouse button. The cells are added to the node.
Figure: A node
tagged with additional column values
Alternatively, you can select the cells in the grid and click on the Tag button (
) to add the cell values to the
currently selected node.
Arranging
the Graph
As you add navigation cases, you may find that you need to move nodes
around, remove selected nodes, zoom and move around in the graph, etc.
You can rearrange the layout of the graph by selecting a node and, with
the left mouse button pressed, drag it around. The arrow and its label
moves with the node.
The toolbar for the graph offers a number of tools to help you with
other tasks.
Figure: The
graph toolbar
All these
tasks can also be accessed through the graph popup menu.
 |
Clicking the Reload
button removes all navigation cases, leaving just the node for the
table you started with. |
 |
You use the
Show/Hide Controls button to control the display of an
Overview control, see below. |
 |
The Zoom
In button lets you zoom into the graph, one step per click. |
 |
The Zoom
Out button zooms the graph out one step with each click. |
 |
Clicking the Zoom
100% button zooms the graph so that all items are shown
with their standard size. |
 |
Use the Fit
button to make all graph items fit in the graph display area. |
 |
The Relayout
button
lays out all graph item with standard positions, distances between
items, etc. This can be useful after making manual changes, such as
removing nodes or tagging nodes. |
 |
The Remove
Node button removes the selected node. It is only enabled
when a navigation case node is selected. |
The Overview control is useful for large graphs that do not fit into
the display area.
Figure: Graph
with the Overview Window displayed
The gray area in the Overview control indicates the portion of the
graph that is currently shown in the display area. You can drag the
gray area around to study other portions of the graph.
To get a larger graph display area, you can put the Overview control in
a separate window. Just uncheck the Docked checkbox.
Exporting
and Printing the Graph
You can also export the graph to an image file or print it. Use the
corresponding toolbar buttons to do this.
 |
Export the graph to a JPG or GIF file. |
 |
Print the graph |
 |
Show a preview of how the graph will be printed |
When you print the graph, you are prompted for information about what
to print (the Graph or the View, i.e., just the portion visible in the
display area) and how many rows and columns to split the printing over
(one page is used for each row/column). See the Export and Print
sections in the Export,
Import and Print section for details.
Copyright © 2007 Onseven Software AB. All rights reserved.
