Use this to check whether a number of columns have the primary key property. This is the case if the corresponding row value combinations appear more than once, or if single row values are NULL. Rows that do not conform to the primary key property are selected.
- In the formulation without select_list, the columns to be checked for the primary key property are selected.
- ROWNUM cannot be used in combination with this statement.
- Verification of the primary key property occurs in the table stated in the FROM clause. It is not until WHERE, GROUP BY, and similar are used on the table with the columns that violate the property.
The following examples relate to this table: