The Sort-Merge-Join algorithm is an effective and widely used algorithm for implementing the important Join operation in database systems. The algorithm is revisited in this paper. It is discovered that sorting both operand relations externally is not necessary in the algorithm. The cost of the algorithm would be reduced greatly if only one operand relation is sorted externally. In order to overcome the shortcomings of the Sort-Merge-Join algorithm, a new Join algorithm called SDC-Join algorithm, is proposed in this paper. The SDC-Join algorithm is a single-relation-sorting based divide-and-conquer algorithm. A parallel version of the SDC-Join algorithm is also presented in the paper. Theoretical analysis and experiment results show that the performance of the SDC-Join algorithm is much higher than that of the Sort-Merge-Join algorithm in both uniprocessor computer systems and parallel computer systems.