1. Question 1

The SELECT statement is called a ______.

• ❌ Table name

• ✅ Query

• ❌ Function

• ❌ Operator

Explanation:
SELECT is a query used to retrieve data.

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2. Question 2

SQL to delete authors with IDs A10 and A11:

• ✅ DELETE FROM AUTHOR WHERE AUTHOR_ID IN (‘A10’, ‘A11’)

• ❌ AUTHOR_ID IS (…)

• ❌ DELETE AUTHOR_ID IS (…)

• ❌ DELETE (‘A10′,’A11’)

Explanation:
Use IN for multiple values:

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3. Question 3

Primary key uniquely identifies each ______.

• ❌ attribute

• ✅ row

• ❌ relation

• ❌ column

Explanation:
A primary key identifies each row (record).

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4. Question 4

SQL command categories: DDL and ______.

• ❌ DIL

• ❌ DUL

• ✅ DML

• ❌ DEL

Explanation:
DDL (structure), DML (data manipulation: SELECT, INSERT, UPDATE).

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5. Question 5

Query that returns number of reps per state:

• ❌ SELECT State, COUNT(State)

• ✅ SELECT State, COUNT(State) FROM Representative GROUP BY State

• ❌ DISTINCT with COUNT incorrectly used

• ❌ DISTINCT only (no counting)

Explanation:
Grouping is required for aggregation.

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6. Question 6

Clause to list cities with 10,000–20,000 residents:

• ✅ WHERE Residents BETWEEN 10000 AND 20000

• ❌ WHERE Residents ARE BETWEEN

• ❌ IN (10000,20000)

• ❌ Residents 10000–20000

Explanation:
BETWEEN gives inclusive range filtering.

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7. Question 7

Retrieve lowest salary:

• ❌ LOWEST()

• ❌ WHERE MINIMUM()

• ✅ SELECT MIN(SALARY) FROM EMPLOYEES

• ❌ MAX()

Explanation:
MIN() returns smallest value.

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8. Question 8

Retrieve product name with lowest price:

• ✅ SELECT PRODUCT_NAME FROM PRODUCTS WHERE UNIT_PRICE = (SELECT MIN(UNIT_PRICE) FROM PRODUCTS)

• ❌ UNIT_PRICE IS LOWEST

• ❌ UNIT_PRICE = MIN

• ❌ SELECT MIN(UNIT_PRICE) only returns number, not product name

Explanation:
Use subquery to match the minimum price.

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9. Question 9

A database cursor:

• ❌ Does not allow updates

• ✅ Enables traversal over records

• ❌ Does not allow DB communication

• ❌ Does not allow tables

Explanation:
A cursor moves row-by-row over query results.

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10. Question 10

Meaning of:

• ✅ df – data frame; Sample – table name ; conn – connection variable

• ❌ Other options

Explanation:
to_sql writes a DataFrame (df) into a database table (Sample) using a DB connection (conn).

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🧾 Summary Table

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