Title: SDB Database Layouts
[SDB](index.html "SDB") does not have a single database layout. This
page is an informal overview of the two main types ("layout2/hash"
and "layout2/index").
In SDB one store is one RDF dataset is one SQL database.
Databases of type layout2 have a triples table for the default
graph, a quads table for the named graphs. In the triples and quads
tables, the columns are integers referencing a nodes table.
In the hash form, the integers are 8-byte hashes of the node.
In the index form, the integers are 4-byte sequence ids into the
node table.
**Triples**
+-----------+
| S | P | O |
+-----------+
Primary key: SPO
Indexes: PO, OS
**Quads**
+---------------+
| G | S | P | O |
+---------------+
Primary key: GSPO
Indexes: GPO, GOS, SPO, OS, PO.
**Nodes**
In the index-based layout, the table is:
+------------------------------------------------+
| Id | Hash | lex | lang | datatype | value type |
+------------------------------------------------+
Primary key: Id
Index: Hash
Hash:
+-------------------------------------------+
| Hash | lex | lang | datatype | value type |
+-------------------------------------------+
Primary key: Hash
All character fields are unicode, supporting any character set,
including mixed language use.