Chess Knight Move

Sid and Al were sitting in a Chinese restaurant.
"Sid," asked Al, "Are there any Jews in China?"
"I don't know," Sid replied. "Why don't we ask the waiter?"When the waiter came by, Al said, "Are there any Chinese Jews?"
"I don't know sir, let me ask," the waiter replied and he went into the kitchen.
He quickly returned and said, "No, sir. No Chinese Jews."
"Are you sure?" Al asked.
"I will check again, sir." the waiter replied and went back to the kitchen.
While he was still gone, Sid said, "I cannot believe there are no Jews in China. Our people are scattered everywhere."
When the waiter returned he said, "Sir, no Chinese Jews."
"Are you really sure?" Al asked again. "I cannot believe there are no Chinese Jews."
"Sir, I ask everyone," the waiter replied exasperated. "We have orange jews, prune jews, tomato jews and grape jews, but no one ever hear of Chinese jews!"