Watch the Example 16 online guitar lesson by Brad Carlton from Guitar Lab: Boogie-Woogie
This example is built from A mixolydian. The chords are A7, D/A, G/A and back to D/A. Notice the move 3 (in A7) to 4 (in G/A). This passage moves back and forth between the "3rd side" of the dominant family to the "sus4 side" of the dominant family. The G/A is actually an A9sus4.