Do you think that one employee's attitude affects your buying decision?

In some cases yes. If I was undecided about a purchase and the shop employee gave me attitude, it would help me decide not to buy. (To be honest, I'd be even more likely to do the same if there was a long queue at the till or in the fitting room. I've been known to put my fruits and vegetables back when the wait for weighing is too long.) However, if I was really keen on the purchase, I'd get over it and just buy it in spite of the bad service, esp. if I knew I couldn't get the same product elsewhere. I'd probably avoid coming to the same shop again though unless I'd absolutely have to. On the other hand, if I get excellent service I rarely walk out of the shop empty-handed because I'd feel bad for the employee if I didn't buy anything after all the lenghts they went into to serve me.

60% yes 

In case I saw something happens made me suspect, I'll be hesitated to buy the product.

And I know well how the companies are very interested in training it's employees on how the attitude should be to put a good impression to their customers.

yes,,

Often as a customer, if the employee does not know the etiquettes of treating  a customer, and giving full ceridable infromation with high courtsy i will not purchase even if it is the last piece in the market.