SQL/MX 2.x Installation and Management Guide (G06.24+, H06.03+)

Understanding and Planning SQL/MX Tables
HP NonStop SQL/MX Installation and Management Guide—523723-004
4-19
Determining When to Use Indexes
B, C), there are three key prefixes: A, AB, and ABC. The prefix ABC corresponds to
the full key, the other prefixes form a partial key.
In this example, COL1 and COL2 are key prefixes from two different indexes. NonStop
SQL/MX uses the indexes to retrieve all the rows that satisfy the predicate that COL2 =
20 or COL1 = 10:
SELECT * FROM T
WHERE COL1 = 10 OR COL2 = 20 ;
Evaluating the query by using the indexes is much more efficient than scanning the
entire table.