Table Lookup by Direct Addressing: From V8 to V9

Table lookup is one of the most, if not the most, important and frequently performed data processing operations. The SAS System supports this assertion with a roster of built-in searching techniques, such as merges, joins, formats, indexes, and search-specific operators and functions. It is therefore all the more surprising that until the advent of Version 9 the fastest, i.e. direct-addressing searching algorithms, such as hashing and bitmapping, have not been available in a built-in form. This gap has been partially covered by SAS programmers crazy enough to hand-code their own hash-based schemes using the power of the SAS Language. In Version 9, however, the situation has finally changed. Not only has it made direct addressing available in the form of a built-in hash table (associative array) object, which can be searched much faster than any other SAS lookup structure, but with it, Version 9 has also introduced the first truly runtime dynamic, memory-resident Data step structure. In this talk, we will get a taste of this new exciting SAS instrument and some cool things it can help us do. We will also see that it does not make hand-coded hashing methods instantly obsolete. Both have their place in a SAS user's repertoire, the choice depending on the data knowledge and programming and/or computer efficiency.