Exam 1.3

Question 1

What language are queries written in

Answer 1

declarative langauge

Question 2

T or F DB optimize efficiency of running queries

Answer 2

T

Question 3

T of F Null values are nuplicates

Answer 3

False null values do not count as duplicates

Question 4

How does inserting into a table atheletes(aid, name , country , sport) work

Answer 4

you do values(x,x,x,x) wher eeach x is a value that belongs to the type specified in atheletes

Question 5

T or F when inserting into table you need to specify the columns you are inserting into

Answer 5

False you can ommit the columns ex Atheletes() if the values are in the correct order that they are listed

Question 6

T of F you can switch order of things inserted into tables

Answer 6

True but only if values inserted also matches

Question 7

how does cross product work between 2 tables

Answer 7

rows in each of the tables will combine with the rows from the other tables

Question 8

How do select statement work under the hood

Answer 8

they are just cross products and then use the constraints to filter out unwanted

Question 9

How to define a view

Answer 9

Create view [viewname] ([vars you want in view])
after all that
as is used then after that is a query

Question 10

T of F view can be directly modifiedd

Answer 10

False they must be dropped and recreated

Question 11

In relational tables when there is one to many how is data stored and primary key represeted

Answer 11

you do not need an extra table you can store foreign key in table representing many side

Question 12

how can participation constaints be shown in relational tables

Answer 12

they will have not null

Question 13

How does ON DELETE NO ACTION work

Answer 13

usually used after foreign keys and makes the foreign key erference not able to be deleted til child is deleted

Question 14

How are weak entities portrayed in tables

Answer 14

they have foreign key to parent element and they have on delete cascade

Question 15

how is a weak entity primary key maintianed

Answer 15

their primary key is the combo of parent and their unique keyw

Question 16

Principles of aggregration

Answer 16

You must keep primary key of all participation sets

Question 17

What is not in SQL

Answer 17

<>

Question 18

How do you define constaints

Answer 18

Constraint [cname]
Check [terms]

Question 19

when does check constraint execute

Answer 19

every time table is modified

Question 20

what does check constraint do for empty relation

Answer 20

evalues to true

Question 21

Where are constraints defined

Answer 21

inside tables

Question 22

What can be used for constraints across multiple functions

Answer 22

assertion and triggers

Question 23

How are assertions created

Answer 23

CREATE ASSERTION [aname]
CHECK ((the assertion))

Question 24

Which are better to use assertions or triggers

Answer 24

triggers because they cost less

Question 25

How doe triggers work

Answer 25

change values depending on if specified changes are made to the dbms

Question 26

Parts of a trigger

Answer 26

event condition action

Question 27

what can update triggers

Answer 27

insert deletion update

Question 28

Syntax for trigger

Answer 28

CREATE TRIGGER [tname] BEFORE UPDATE ON [tableName] FOR EACH ROW DECLARE [anything you want] BEGIN END;

Question 29

Cons of triggers

Answer 29

They can be recursive making a bunch of them hard to predict Mutated trigger error when table modifies same table being modified