Added section on querying - #64 [skip ci]

README.md

@@ -145,6 +145,22 @@ To index many different values of `category_id`, consider [partitioning](https:/
 CREATE TABLE items (embedding vector(3), category_id int) PARTITION BY LIST(category_id);
 ```
 
+## Querying
+
+Use a `SELECT` clause to get the distance
+
+```sql
+SELECT embedding <-> '[3,1,2]' AS distance FROM items;
+```
+
+Use a `WHERE` clause to get rows within a certain distance
+
+```sql
+SELECT * FROM items WHERE embedding <-> '[3,1,2]' < 100;
+```
+
+Note: Combine with `ORDER BY` and `LIMIT` to use an index
+
 ## Performance
 
 To speed up queries without an index, increase `max_parallel_workers_per_gather`.