No. A column with a large percentage of NULL values should not be indexed because the speed of accessing these rows degrades when the value of a large percentage of rows is the same.
No. The main purpose of an index is to enhance data retrieval speed; although a unique index stops duplicate values in a table.
False. The main reason for composite indexes is for two or more columns in the same table to be indexed.
Cardinality refers to the uniqueness of the data within a column. The SSN column is an example of such a column.
The index might not be of any use for performance issues, but the unique index would keep referential integrity intact.
A full table scan occurs.
The most restrictive clause(s) should be evaluated before the join condition(s) because join conditions normally return a large number of rows.
The CONNECT TO statement establishes this.
The CASCADE option allows the schema to be dropped if there are still objects under that schema.
The CREATE SCHEMA command creates a schema.