Logical and Physical Query Processing

Question 1

What are the two processing sides of T–SQL?

Answer 1

Logical processing and physical processing.

SQL Server 70-461 01-02

Question 2

What is logical query processing?

Answer 2

The conceptual interpretationof the query that defines the correct result. It determines “what” will be returned.

SQL Server 70-461 01-02

Question 3

What is physical query processing?

Answer 3

Processing of the query by the database engine. It determines “how” it will be returned.

SQL Server 70-461 01-02

Question 4

What can optimization do?

Answer 4

It can rearrange steps from logical query processing or remove steps altogether, but only as long as the result remains the one defined by logical query processing.

SQL Server 70-461 01-02

Question 5

What is the “keyed–in order” of the main query clauses?

Answer 5

1. SELECT
2. FROM
3. WHERE
4. GROUP BY
5. HAVING
6. ORDER BY

SQL Server 70-461 01-02

Question 6

What is the logical query processing order of the main query clauses?

Answer 6

1. FROM
2. WHERE
3. GROUP BY
4. HAVING
5. SELECT
6. ORDER BY

SQL Server 70-461 01-02

Question 7

In what order are the attributes in the SELECT clause processed?

Answer 7

Conceptually they are all processed at the same time.

SQL Server 70-461 01-02

Question 8

If you assigned an alias to an attribute or expression in the SELECT clause, can you use that alias in another expression in the SELECT clause?

Answer 8

No, because conceptually the attributes are all processed at the same time so the alias doesn’t exist yet to be used.

SQL Server 70-461 01-02

Question 9

How are expressions that appear in the same logical query processing phase processed?

Answer 9

All expressions that appear in the same logical query processing phaseare conceptually processed at the same point in time

SQL Server 70-461 01-02