Generate statistics is used to gather statistics about each table column’s proportion of duplicate values, minimum values, maximum values, null values, unique values, and updates the system catalog tables.
The difference between ‘generate statistics’ and ‘generate express statistics’ is based on how the column uniqueness is calculated. The ‘generate express statistics’ calculates estimated dispersion values based on the sampling of rows in the table. ‘Generate express statistics’ uses approximation in generating the stats whereas ‘generate statistics’ uses all the rows in the table.
