Database Systems: All Quizes
3 steps to index lookup
1. tree traversal 2. follow leaf node chain 3. fetch table data
HTTP response for OK
200
Benefits of data locality
Bandwidth reduction, speed NOT Regulation, Resiliency through sharding, Cost
Index works better with: - columns updated frequently - columns with few NULLS, searched frequently - columns with mostly numeric data - all columns
Columns with few NULLS searched frequently
XAMPP stands for
Cross platform, Apache, MySQL, PHP, Perl
XML, JSON, YAML are formats for...
Data Serialization
What does the Hadoop distributed system provide over other file systems
Data locality
ERD stands for
Entity Relationship Diagram
Every node (except leaf) in a B-tree has 2 children (T/F)
False
I can only have 1 table in a db (T/F)
False
HDFS, MapReduce, and Pig are related to...
Hadoop
What is the most common type of join?
INNER JOIN
With SQL, how can you insert "Olsen" as the "LastName" in the "Persons" table?
INSERT INTO Persons (LastName) VALUES ('Olsen')
I want to find items that are in Table A AND Table B. The operator that I would use is:
INTERSECT
How does indexing affect SELECT and UPDATE tasks
Indexing makes SELECT faster, but UPDATE slower
What programming model does Hadoop follow
MapReduce
What is data locality?
Move computation to the data, not data to the computation (traditional sever/client moves data to computation)
The column in a database table that uniquely identifies the record is a:
Primary Key
An attribute or group of attributes that uniquely identifies an instance of the entity in an ERD is the:
Primary key (Composite or otherwise)
In Hadoop, sorted output of a Mapper is sent to the...
Reducer
SELECT price, COUNT(*) FROM app_list GROUP BY price;
Returns a count of the total number of apps for each price in the table
With SQL, how do you select all the records from a table named "Persons" where the "LastName" is alphabetically between (and including) "Hansen" and "Pettersen"?
SELECT * FROM Persons WHERE LastName BETWEEN 'Hansen' AND 'Pettersen'
Which SQL statement is used to return only different values?
SELECT DISTINCT
A language for writing queries or "asking questions of the database" to retrieve the desired data is:
SQL
Model-View-Controller
Separate the View (UI) from the controller (code) and the model (database). Each part should be able to be changed separately from the other 2.
SQL stands for
Structured Query Language
An instance of an entity is a ROW in a table (T/F)
True
I could connect remotely to a database (or DBMS) on another computer via the Internet (T/F)
True
How can you change "Hansen" into "Nilsen" in the "LastName" column in the Persons table?
UPDATE Persons SET LastName='Nilsen' WHERE LastName='Hansen'
"StudentIDNumber" in a table is likely: -a column in a 'Student' table -A 'one to one' cardinality -A relationship -a row in a 'Student' table
a column in a 'Student' table
In a 'student' entity or table, 'last_name' would be considered: - primary key - foreign key - attribute - row
attribute
SQL operator for multiple "if" statements
case
Which is NoSQL: - Oracle - MariaDB - couchDB
couchDB
IN SQL "<>" is the same as:
not equals
Which doesn't exist: - perc - round - avg - sum
perc
Pick the one that looks like an API key - asdflk2342r2l342hk2j423 - 200 OK - Content-type: text/html; charset=UTF-8 - POST /codeacademy/learn-http HTTP/1.1
sdfklasjg234k2j34l2h
SELECT customerid, customername, companyname, city FROM customers WHERE customerid <> '115' AND city = (SELECT city FROM customers WHERE customerid = '115');
show me the records for customers who are in the same city as customer 115
I want to create storage of the students in a class, holding their ID numbers, names, and grades. I will build a(n): - table - recordid - field - sql query
table
