Search Conditions for Single-Column Inverted Columns
If you specify
search conditions for single-column inverted columns, the search strategy is determined by the system as specified in the table.
Search Condition |
Search Strategy |
Equality Condition for a single-column inverted column |
Only those lines whose keys are contained in the associated inversion list are accessed. |
IN condition for a single-column inverted column |
The system accesses the lines whose keys are contained in the inversion lists. |
Multiple equality conditions for different, single-column inverted columns |
The system determines the intersection of the inversion lists concerned. The system accesses only the lines whose keys are contained in all of the specified inversion lists. |
Area Conditions
There is only one condition ( <, <=, >, >=) for one of the two area limits (upper or lower limit). |
The system accesses the lines whose keys are contained in the inversion lists that were determined by the area. |
Area conditions Both area limits are specified. It is irrelevant to the selection of the search strategy whether this specification is made using a BETWEEN operator or using two conditions ( <= or >=) for the same column linked by AND. |
The system accesses the lines whose keys are contained in the inversion lists that were determined by the area. |
Several area conditions linked by AND There is at least one area restriction for one single-column inverted column, and, for up to 19 other single-column inverted columns, there is one comparison condition for each column, or at least one area restriction. |
A logical inversion list, that does not necessarily exist physically, is created for all columns. The intersection of these inversion lists is formed. The system accesses only the lines whose keys are contained in all of the inversion lists. |
In the case of the equality/IN conditions and the area conditions, there are also queries for which it is not necessary to access the lines, as all required values are contained in the inversion list(s).
See also:
Examples: Search Conditions for Single-Column Inverted Columns