Question

I need to save measures coming from devices into a SQL database (SQL Server 2008). Each device gives, at a specific time, the same array of measures. An array is composed of 80 measures, that can be grouped.

To resume, at a specific time t(x), I have the following data (t(x) considered as one “session” of measures):

• t(0): DeviceID, DateTime, 80 measures
• t(1): DeviceID, DateTime, 80 measures
• …

A device produces, in a session of measures t(x), 8 sets of same type of 10 measures (a, b, c, d, e, f, g, h, i, j) (a, b ,c … representing the type of measures as int, float, double, etc..) corresponding of 8×10=80 measures in total.

Example:

• set N°1 can be (10, 2, 3.2f, 4.76, “Data1”, 3, 2, 2.2, 5.6f, 10.0f)
• set N°2 can be (2, 4, 31.2f, 4.23, “Data2”, 1, 1, 3.2, 2.2f, 2.1f)
• ….
• set N°8 can be (10, 7, 1.1f, 2.35, “Data8”, 8, 1, 2.1, 2.1f, 8.2f)

Note: the number of sets of measures, 8, will not change.

I would like to know what can be the best design of table(s) to handle these measures (insert, select, delete, no update)?

I thought about these possibilities:

• It can be one table with 82 columns.
• It can be one main table (DeviceID, DateTime) and 8 sub tables representing the 8 set of measures.
• It can be one main table (DeviceID, DateTime) and 1 sub table that can have one set of measure, and a type to indicate which set of measures.

Answer 1

If every “session” consists of (8, either stable or not) number of sets where every “set” consists of (10, not-to-change) number of measurements (of possibly different types), I’d choose one table with fields:

CREATE TABLE deviceData
  ( deviceID INT
  , sessionID INT
  , setID INT
  , a int
  , b int
  , c int
  , d int
  , e int
  , f int
  , g int
  , h float
  , i float
  , j double
  , PRIMARY KEY (deviceID, sessionID, setID)
  ) ;

You can also have a deviceSession, where the date or datetime field for every session can be stored:

CREATE TABLE deviceSession
  ( deviceID INT
  , sessionID INT
  , measureTime DATETIME
  , PRIMARY KEY (deviceID, sessionID)
  ) ;

I would also add a foreign key constraint from deviceData to this table:

ALTER TABLE deviceData
  ADD FOREIGN KEY (deviceID, sessionID) 
        REFERENCES deviceSession(deviceID, sessionID)

And every INSERT could be a transaction that inserts one row at deviceSession and 8 rows at deviceData.

---

Sample data:

+----------+-----------+-------+---+---+----+----+---+---+----+-----+-----+-----+
| deviceID | sessionID | setID | a | b |  c |  d | e | f |  g |  h  |  i  |  j  |
+----------+-----------+-------+---+---+----+----+---+---+----+-----+-----+-----+
|    1     |     1     |   1   | 7 | 8 | -3 | 17 | 0 | 3 | -6 | 7.0 | 4.3 | 6.9 |
|    1     |     1     |   2   | 4 | 6 |  2 | 12 | 3 | 0 | -6 | 8.0 | 4.4 | 6.7 |
|    1     |     1     |   3   | 5 | 5 | -1 |  7 | 2 | 0 | -6 | 7.5 | 4.9 | 7.4 |
.................................................................................
|    1     |     1     |   8   | 0 | 9 | -6 | 29 | 0 | 7 | -6 | 7.8 | 6.3 | 7.3 |
|    1     |     2     |   1   | 5 | 4 | -6 | 29 | 9 | 7 | -6 | 7.9 | 6.3 | 4.3 |
|    1     |     2     |   2   | 4 | 3 |  2 | 12 | 3 | 0 | -6 | 8.0 | 4.4 | 6.7 |
|    1     |     2     |   3   | 5 | 5 | -1 |  8 | 2 | 0 | -6 | 7.5 | 4.9 | 7.4 |
.................................................................................
|    1     |     2     |   8   | 0 | 4 | -6 | 20 | 5 | 7 | -6 | 7.6 | 6.3 | 7.3 |
|    1     |     3     |   1   | 4 | 6 |  2 | 17 | 0 | 3 | -6 | 7.0 | 4.3 | 6.9 |
.................................................................................
.................................................................................
|    2     |     1     |   1   | 2 | 2 | -2 | 12 | 0 | 2 | -2 | 2.0 | 2.2 | 2.2 |
|    2     |     1     |   2   | 6 | 7 | -9 | 12 | 0 | 2 | -2 | 2.0 | 8.2 | 7.2 |
.................................................................................
.................................................................................
+----------+-----------+-------+---+---+----+----+---+---+----+-----+-----+-----+