Histogram for column: "city" Column datatype: varchar(20) Requested step count: 20 Actual step count: 20 Sampling percent: 0 Out of range histogram adjustment: DEFAULT
optdiag first prints summary data about the histogram, as shown in Table 2-6.
Row label |
Information provided |
---|---|
Histogram for column |
Name of the column. |
Column datatype |
Datatype of the column, including the length, precision and scale, if appropriate for the datatype. |
Requested step count |
Number of steps requested for the column. |
Actual step count |
Number of steps generated for the column. This number can be fewer than the requested number of steps if the number of distinct values in the column is smaller than the requested number of steps. |
Sampling percent |
Percentage of table data sampled to produce the histogram. Value range is from 0 – 100. |
Out of range histogram adjustment |
Indicates whether the column’s histogram is to be adjusted to assign a selectivity value for out-of-bounds search arguments on the column. Value is one of on, off, or default. This row appears along with histogram information only for global column statistics, not at the partition level. |
Histogram output is printed in columns, as described in Table 2-7.
Column |
Information provided |
---|---|
Step |
Number of the step. |
Weight |
Weight of the step. |
(Operator) |
<, <=, or =, indicating the limit of the value. Operators depend on whether the cell represents a range cell or a frequency call. No heading prints for this column. |
Value |
Upper boundary of the values represented by a range cell, or the value represented by a frequency count. |