Adds MCQs.

database/mcqs/02-integrity-er-diagram.md

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+# Questions
+1. Joe Bloggs is helping us build Scaler. He is trying to delete some batches but the database throws an error that the batch is used by a tuple in another table. Which type of integrity constraint is being enforced here?
+    >A. User-defined integrity \
+    B. Domain integrity \
+    C. Entity integrity \
+    D. Referential integrity
+---
+2. Which of the following is not an example of domain integrity constraints?
+
+    >A. Validating that input is correct data type \
+    B. Ensuring value is not null if a non-nullable column \
+    C. Making sure each row is unique \
+    D. Checking if the value exceeds maximum length
+---
+3. Joe Bloggs is taking some time off to build his house. A house can have many rooms. What is the cardinality of house to room?
+    >A. One to Many (1:m) \
+    B. One to One (1:1) \
+    C. Many to Many (m:n)
+---
+4. Let us say a house has a house_id and a room has room_id.
+Given the cardinality of house to room, which is the ideal place to store their relationship i.e. reference?
+    >A. room_id in house \
+    B. Separate table for room_id and house_id \
+    C. Array of room_ids in house \
+    D. house_id in room
+
+---
+# Answers
+1. D. `Referential integrity`
+2. C `Making sure each row is unique`
+3. A `One to Many (1:m)`
+4. D `house_id in room`

database/mcqs/03-normalisation-acid.md

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+# Questions
+1. Joe Bloggs is creating a social media today. However, Joe has kept user and group information in the same table. Now whenever Joe removes a user, the group information is also gone. Which type of anomaly is this?
+    >A. Insertion \
+    B. Updation \
+    C. Deletion
+---
+2. A user has an ID, name, email and group ID. One user can only have one email and it is unique.
+Which of the following dependencies is not correct?
+
+    >A. ID -> NAME \
+    B. EMAIL -> NAME \
+    C. EMAIL -> GROUP ID \
+    D. NAME -> GROUP ID
+---
+3. Joe has created a table for group members where the columns are `Group ID, User ID, Rating, Group Name`. The primary key here is `Group ID, User ID`.
+Which type of functional dependency exists?
+    >A. No functional dependency \
+    B. Transitive \
+    C. Partial
+---
+4. Joe has identified that one of his tables does not satisfy 1NF constraints. Which of the following types of ERD attributes are allowed under 1NF?
+    >A. Composite \
+    B. Multivalued \
+    C. Derived \
+    D. Index
+
+---
+# Answers
+1. A. `Deletion`
+2. D `NAME -> GROUP ID`
+3. C `Partial`
+4. C `Derived`