The Foundations of Schema Design in CockroachDB Exam Answers

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The Foundations of Schema Design in CockroachDB Exam Answers:

Quiz 1:

Question 1: Which data type would be useful if you wanted to store the time of day with an offset from UTC?

• now()
• TIME
• TIMESTAMPTZ

Question 2: When working with the DECIMAL data type, which of the following represents the count of digits to the right of the decimal point?

• Scale
• Measure
• Precision

Question 3: In CockroachDB, which of these data types is useful if you need to limit the number of characters stored in a given column?

• STRING(n)
• BYTES
• VARCHAR

Quiz 2:

Question 1: Which feature of CockroachDB lets the database set the current time rather than requiring the client to set this information?

• TIMESTAMPTZ
• TIME
• now()

Question 2: Which feature of CockroachDB helps sort STRING values based on language-and country-specific rules?

• STRING(n)
• GEOGRAPHY
• Collation

Question 3: Which data type would be useful if you were looking to store airport locations in North America in latitude and longitude?

• GEOGRAPHY
• TIMETZ
• GEOMETRY

Quiz 3:

Question 1: Which of the following would be a good use case for a JSON column?

• You need to import JSON data from a third party API
• You want to store a record of every single video game action ever taken by a player in one JSON object
• You’re storing data from an app and you know all of the fields and data types ahead of time

Question 2: Which of the following would be a good use case for an ARRAY column?

• You need to store 3-dimensional coordinates for player locations in a game in sub-ARRAYs like so: [ [23, 18, 5], [19, 4, 10], [1, 25, 8] ]
• You need to store a user’s name as a STRING, age as an INT, and test score as a FLOAT all together in one column
• You need to store a list of phone numbers associated with a user’s account

Question 3: What’s one advantage of using an inverted index?

• They can help avoid the need for full table scans when querying for a matching key: value pair in a JSON column.
• Inverted indexes are extremely compact, increasing the efficiency of writing to a JSON column.
• They increase the efficiency of queries that use less than or greater than

Question 4: What is the purpose of a computed column?

• They expose data generated from other columns by an expression.
• They store a homogeneous list of data in every row.
• They separate each field in a JSON object into a unique index entry.

Quiz 4: Hash

Question 1: When should you hash shard an index? Check all that apply.

• When all candidate index keys are monotonically increasing
• When you’re using a composite index with a TIMESTAMPTZ column as the second column
• When you’re running a 3-node cluster but are ready to scale out
• When there are many null values in the column
• When the column has only a few possible values (such as a BOOLEAN)

Final Assessment:

Question 1: You have a table that stores status updates from an autonomous vehicle with the following schema:

moving BOOLEAN,

check_in TIMESTAMPTZ,

status JSON

Here are the first three rows of this table:

moving            |          check_in         |  status

——————+—————————+——————————————-

TRUE              | 2021-07-10 06:19:03-03:00 | ‘{“velocity”: “10”, “heading”: “145.5”}’

TRUE              | 2021-07-10 06:19:07-03:00 | ‘{“velocity”: “12”, “heading”: “147”}’

TRUE              | 2021-07-10 06:19:11-03:00 | ‘{“velocity”: “15”, “heading”: “149”}’

Of the following options, what would be the best primary key for this table?

• Use the status column as the primary key
• Create a hash sharded primary key with the check_in column
• Create a compound primary key that includes the status column as the leading column and the check_in column

Question 2: When working with the DECIMAL data type, which of the following represents the maximum count of digits both to the left and right of the decimal point?

• Precision
• Scale
• Accuracy
• (n)

Question 3: You have a table that stores a history of alerts received for a monitoring system with the following schema:

alert_code INT,

alert_time TIMESTAMPTZ,

device_id STRING

Here are the first three rows of this table:

alert_code | alert_time |  device_id

—————–+—————————+—————–

404              | 2021-08-26 12:39:35-05:00 | A300-432

502              | 2021-08-26 12:39:46-05:00 | A300-432

404              | 2021-08-26 12:39:48-05:00 | C202-859

Of the following options, what would be the best primary key for this table?

• Create a compound key with device_id as the leading column and the alert_time column
• Create a hash sharded primary key with just the alert_time column
• Create a separate UUID column to use

Question 4: You have a 7 node cluster with 1,000,000 rows between 9 tables, one of which has a TIMESTAMP column. How many buckets should the hash sharded index on that column have?

• 3
• 5
• 7
• 9
• 11

Question 5: Which of these is a benefit of using the now() function for a default column value?

• It can display a TIMESTAMP with more digits than the application
• It provides accuracy through the implementation of atomic clocks on the cluster
• It allows the database to be the source of truth for date and time

Question 6: What data type or feature of CockroachDB type would be useful if you are looking to display green space in a city as polygons on a city map, which is small enough that you don’t need to worry about the curvature of the Earth?

• GEOMETRY
• Collation
• GEOGRAPHY

Question 7: What data type or feature of CockroachDB might you use instead of a definite table schema if you were experimenting with (and frequently revising) a table’s structure during application development?

• The EXPERIMENTAL flag
• BYTES
• JSON

Question 8: Which of the following should be avoided (or otherwise mitigated) when choosing an index key with CockroachDB?

• Letting the database assign UUIDs to a row, which are then used as the primary key
• Using a compound index key
• Using the TIMESTAMP data type as the first column of an index

Question 9: What is a feature of CockroachDB that you might use if you needed to regularly find purchases less than $100 and the purchase information was stored in a field in a JSON column?

• Computed Column with a secondary index
• A regular secondary index on the JSON column
• Inverted Index

Question 10: Which feature of CockroachDB would be helpful if you were building a language learning app and needed a way to sort words from a given language based on the language’s alphabetical sorting rules?

• STRING
• Collation
• GEOGRAPHY
• VARCHAR

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