| 摘要 |
A method, computer system, and computer program are claimed for selecting rows from first and second tables each having rows containing values in columns. In at least the first table, the rows are divided into partitions at least one of which is populated by one or more rows. The method, computer system, and computer program include (a) defining a subset of the populated partitions of the first table that excludes at least one populated partition of the first table, (b) creating a file context, which stores at least location data for a row and a first value associated with the row, for each populated partition in the subset of the populated partitions of the first table, (c) determining the lowest first value stored by the file contexts for the first table, (d) identifying rows with a particular first value by at least reading the file contexts of the first table, and (e) repeating a through d until the subsets of the populated partitions of the first table have included all the populated partitions of the first table.
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