@jason1028,
Setting exploded property to true will explode a slice of pie/doughnut on chart-render.
As you are reading data from database, you can add exploded property by checking the label. Please refer the code-snippet below. Adding the below snippet just before calling chart.render() should work fine in this case.
for(var i = 0; i < chart.options.data[0].dataPoints.length; i++)
if(chart.options.data[0].dataPoints[i].label === "Visa")
chart.options.data[0].dataPoints[i].exploded = true;
—-
Manoj Mohan
Team CanvasJS