optdiag column-level statistics include:
Statistics giving the density and selectivity of columns. If an index includes more than one column, optdiag prints the information described in Table 6-6 for each prefix subset of the index keys. If statistics are created using update statistics with a column name list, density statistics are stored for each prefix subset in the column list.
A histogram, if the table contains one or more rows of data at the time the index is created or update statistics is run. There is a histogram for the leading column for:
Each index that currently exists (if there was at least one non-null value in the column when the index was created)
Any indexes that have been created and dropped (as long as delete statistics has not been run)
Any column list on which update statistics has been run
There is also a histogram for:
Every column in an index, if the update index statistics command was used
Every column in the table, if the update all statistics command was used
optdiag also prints a list of the columns in the table for which there are no statistics. For example, here is a list of the columns in the authors table that do not have statistics:
No statistics for column(s): "address"
(default values used) "au_fname"
"phone"
"state"
"zipcode"
