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How-to-get-result-set-suitable-for-graph-visualisation.md
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# How to get result set suitable for graph visualisation # How to get result set suitable for graph visualisation
There are some [requirements][1] for result sets if you want to build a graph. There are some [requirements for result sets][1] if you want to build a graph.
Here is an example of building a query that returns a result set appropriate for graph visualisation. Here is an example of building a query that returns a result set appropriate for graph visualisation.
Let's say, you have 2 tables: Let's say, you have 2 tables:
@@ -39,9 +39,10 @@ SELECT json_object('object_type', 1)
FROM student FROM student
``` ```
Note that we included `student` table twice. That is because the table contains not only students but also their relationship to houses. Note that we included `student` table twice. That is because the table contains not only students but also their relationship to houses.
So the first union will be used as node records and the second one - as edges. So the records from the first union of `student` will be used as nodes and from the second one - as edges.
Then we need to provide an ID for each node. For students - `id` and for houses - `name`: Then we need to provide an ID for each node. Let's put it in `node_id` field.
The `node_id` value for students is taken from `id` column and for houses - from `name`:
```sql ```sql
SELECT json_object('object_type', 0, 'node_id', name) SELECT json_object('object_type', 0, 'node_id', name)
@@ -54,8 +55,7 @@ SELECT json_object('object_type', 1)
FROM student FROM student
``` ```
Each edge record must specify where it starts and where it ends. Let's provide it as `source` and `target`. Each edge record must provide a node id where the edge starts and where it ends. Let's put it in `source` and `target`:
Provide values that are used as node IDs. In our case it's house names and student IDs:
```sql ```sql
SELECT json_object('object_type', 0, 'node_id', name) SELECT json_object('object_type', 0, 'node_id', name)
@@ -67,9 +67,9 @@ UNION ALL
SELECT json_object('object_type', 1, 'source', house, 'target', id) SELECT json_object('object_type', 1, 'source', house, 'target', id)
FROM student FROM student
``` ```
Basically, that is enough to build a graph. But it won't be meaningfull without lables. Basically, that is enough to build a graph. But it won't be meaningful without labels.
Also, it would be nice to distinguish house nodes from student nodes e.g. by color. Also, it would be nice to distinguish house nodes from student nodes by color.
Let's put additional fields - `label` and `type` that can be used in graph styling. Let's put additional fields `label` and `type` that can be used in graph styling.
```sql ```sql
SELECT json_object('object_type', 0, 'node_id', name, 'label', name, 'type', 'house') SELECT json_object('object_type', 0, 'node_id', name, 'label', name, 'type', 'house')
@@ -101,5 +101,5 @@ Run the query, the result set will look like this:
| {"object_type":1,"node_source":"Ravenclaw","target":4} | | {"object_type":1,"node_source":"Ravenclaw","target":4} |
| {"object_type":1,"node_source":"Hufflepuff","target":5} | | {"object_type":1,"node_source":"Hufflepuff","target":5} |
[1]: ./graph [1]: ./graph#requirements-for-result-set
[2]: https://sqlite.org/json1.html#jobj [2]: https://sqlite.org/json1.html#jobj