Consider the table shown in Figure 1.5, repeated here for convenience: Give three reasons why it cannot possibly represent a relation. By the way, this table is supported by SQL, and the three reasons represent some of SQL’s serious and far-reaching deviations from relational theory.

EXPERT ANSWER

Question1

1.Duplicate rows

2.null values

3.duplicate column names

Question2

1. Collection of columns

2. Row as a set of values

3. Column as a set of values

Explanation:

Question1

1. A table cannot have duplicate rows. The first and last rows are duplicates.

2) A table cannot contain NULL values. In a relational database, all values must be non-null. There are values missing in the table.

3. A table cannot have columns with duplicate names. The first and last columns have the same name A.

Question2

1) SQL does not support the relational model’s concept of a table being composed of rows. Instead, SQL views a table as a collection of columns.

2) SQL does not support the relational model’s concept of a column being composed of a single value. Instead, SQL views a column as a set of values.

3) SQL does not support the relational model’s concept of a row being composed of a single value. Instead, SQL views a row as a set of values.