What does it mean for a query language to be declarative?
The language specifies the process of how to obtain the data.
The language specifies what data to obtain.
A language specific declaration of data types in order to define the method of data retrieval.
The language specifies both the process of how to obtain the data and specifies what data to obtain.
Use the following table named "user_table" to answer the next 2 problems.
userId
username
email
1
admin
admin@corporate.moe
2
h4xor
1337@rawr.cte
How would you go about querying the entire username column (however many)?
SELECT user_table FROM username
SELECT username FROM userId WHERE *
SELECT username FROM user_table WHERE userId=1
SELECT username FROM user_table
How would you go about querying the entire database table (please refer to question 2's table)?
SELECT username, email FROM userId
SELECT FROM WHERE user_table
SELECT * FROM user_table
SELECT user_table FROM *
What is the global indexing table?
An index table in order to keep track of data records within one machine.
An index table in order to keep track of a given data type that might exist within multiple machines.
A global table that uses a specific technique called indexing and the table uses an index as the primary key.
An index table in order to keep track of a given data type that might exist within one machine.
What are the three computing steps of a semi-join?
Project, Ship, Reduce
Project, Decompose, Send
Index, Join, Display
Query, Join, Display
None Applicable
What is the purpose of a semi-join?
Increase the speed of the join for trade-off of increased data transmission cost.
Increase the efficiency of sending data across multiple machines.
Another name for join: an operation to combine two tables by column.
What is a subquery?
A query statement within another query.
A short query than normal.
An alternative query that acts as a substitute for another query.
What is a correlated subquery?
A type of query that contains a relationship between a variable attribute x and a variable attribute y. The two variables have a dependent relationship causing a correlation.
A type of query that contains a subquery that requires information from a query one level up.
A type of query that requires two tables in order to calculate values.
What is the purpose of GROUP BY queries?
Enables calculations based on specific columns of the table.
Required before you can use functions like AVG, SUM, MIN, MAX, COUNT.
Enables queries within queries.
Consider the following generic statement for questions 10-12:
db.<collection>.find(<query filter>, <projection>).<cursor modifier>Which part of the statement would reflect that of the FROM statement in SQL as illustrated in the lecture?
<collection>
<projection>
<query filter>
<cursor modifier>
Which part of the statement would reflect that of the SELECT statement in SQL as illustrated in the lecture?
<query filter>
<collection>
<cursor modifier>
<projection>
Which part of the statement would reflect that of the WHERE statement in SQL as illustrated in the lecture?
<collection>
<projection>
<cursor modifier>
<query filter>
A sample part of the data structure is as follows:
{ _id:1, userIndex: 10, email: “arealeamil@notreallu.asd", retainRate:2}What would be the most likely statement that we would need to grab email info for user indexes greater than 24?
db.email.find({userIndex:{$gt:24}}, {email:1, _id:0})
db.userIndex.find({email:{$gt:24}}, {_id:0})
db.userIndex.find({email:{$lte:24}}, {_id:0})
db.email.find({userIndex:{$lte:24}}, {email:1, _id:0})
What does it mean to have a _id:0 within our query statement?
Tell MongoDB not to return a document id.
Grab as many objects as possible.
Grab the first object in the results.
Does not have an effect, simple convention left for compatibility issues.
