OpenAccess SDK SQL engine and IP interaction : Example database

Example database

This example has a current value table that is called CURVALUE and has schema as defined in the following table.

Table 4: Schema of the CURVALUE table
Column Name	Description
NAME	Name of the tag (primary key)
INTVAL	Integer value
FLOATVAL	Floating point value
TIME	The time the data was collected

Assume the following values in the database:

NAME	INTVAL	FLOATVAL	TIME
SCOTT	1	100.0	1999-12-10 12:00:30
TOM	1	101.0	1910-01-01 15:00:00
BOB	2	100.0	2010-02-02 01:00:00
xxx	x	x	2000-01-01 09:00:00
JOE	4	102.0	Joe who?

It is assumed that data in the CURVALUE table can be accessed in the following ways:

• A row of data can be retrieved by specifying a value for NAME

• A list of NAME values can be retrieved by specifying a pattern to match

Assume that no other way of locating and accessing the data is available and assume that you want to perform the following query on this data source:

   SELECT NAME, VALUE FROM CURVALUE WHERE (NAME=SCOTT OR NAME=TOM OR NAME=JOE) 

   AND FLOATVAL > 100.0

The result of this query should be:

NAME	FLOATVAL
TOM	101.0
JOE	102.0

First, you learn about the processing performed by the OpenAccess SDK SQL engine and the IP to implement this query without doing any optimization. Then, you learn about the processing performed by the OpenAccess SDK SQL engine and the IP to implement this query with optimization. These two examples give you an idea as to how the OpenAccess SDK SQL engine and the IP work together to execute a query.