Query Optimization

When querying data, which is the best way to phrase the SELECT Statement?

• It makes no difference

• By making use of SELECT and then manually defining each field

• By making use of SELECT *

Does DISTINCT improve SELECT query execution performance?

• Yes, it removes quantity of data being queried

• No, It has no effect

• Yes, it enables the use of indexes

• No, DISTINCT is actually an expensive separate GROUPING statement

Which is the more expensive filtering Keyword

• AND

• OR

• They are both the same

• It is not possible to calculate

Why is it inadvisable to use the LIKE filter? (for using %wildcards%)

• It is the same as using the = sign

• It prevents the use of indexes

• It forces the DB to search through the whole field for each row

• its results can be untrustworthy

How does adding an index assist in efficient queries?

• Creates an AI agent to assist the Query Optimizer

• Creates a hash table that points to the data

• Creates a new instance of the database

• It has no effect

What is the downside of adding an index to the database?

• It adds a performance overhead to INSERT and DELETE

• The Query Optimizer may get confused

• Uses extra disk space

Our database usage is measured in DTU (Database Transfer Units). But how is DTU calculated?

• The maximum of Compute and Data IO

• The amount of data units that is transferred

• Not even Microsoft knows

What happens when we hit 100% of DTU?

• Nothing happens

• We get DoS from the database

• Our DB usage will be throttled

• We get a surcharge expense for over usage

What effect does it have on another BL when a single BL hits 100% DTU

• There is no effect - they each have the own DTU

• Other BL databases also immediately give DoS

• It takes available DTU from others

What is the performance effect of including subqueries (at scale)? (see image for example)

• Downgrade in performance.

• Improvement in performance.

• It makes no difference.