Operators

The sample DataBlade module defines the following four operators that can be used on columns of data type MyShape, MyBox, MyCircle, and MyPoint in the WHERE clause of a query:

• Overlap returns a Boolean value to indicate whether two shapes intersect or overlap.
• Equal returns a Boolean value to indicate whether two shapes are the same or occupy the same space.
• Contains returns a Boolean value to indicate whether the first shape contains the second shape.
• Within returns a Boolean value to indicate whether the first shape is within or is contained by the second shape.

These operators, of course, are also the strategy functions defined by the operator class.

The following example uses the Overlap operator to return all the boxes in the box_tab table that overlap a box whose lower-left coordinate is (30,20) and upper-right coordinate is (60,50):

SELECT * FROM box_tab
WHERE Overlap (boxes, 'box(30,20,60,50)' );

id     1 
boxes  box(10,10,40,40)  

The following example uses the Contains operator to return all the boxes in the box_tab table that contain a box whose lower-left coordinate is (-5,-10) and upper-right coordinate is (2,5):

SELECT * FROM box_tab
WHERE Contains (boxes, 'box(-5,-10,2,5)' );

id     2 
boxes  box(-10,-20,5,9)