2. Write a SQL query to solve Question-2-2 (the second sub-question). 3. Write a SQL query to solve Question-2-3 (the third sub-question). 4. Write a SQL query to find the name of oldest sailors for each rating level. 5. Find the average age of sailors for each rating level that has at least two sailor 6. Write a SQL query to find the average number boats reserved by different sail 7. Write a SQL query to find the names of sailors who reserved all non-blue boa 8. Write a SQL query to find the name of the boat that is most popular one. 9. What does the following two queries do? SELECT sid SELECT sid FROM s WHERE rating > all ( SELECT rating FROM s s2 FROM s WHERE rating> any ( SELECT rating FROM s s2 WHERE s2.sname='Bob’)) WHERE s2.sname='Bob’)
2. Write a SQL query to solve Question-2-2 (the second sub-question). 3. Write a SQL query to solve Question-2-3 (the third sub-question). 4. Write a SQL query to find the name of oldest sailors for each rating level. 5. Find the average age of sailors for each rating level that has at least two sailor 6. Write a SQL query to find the average number boats reserved by different sail 7. Write a SQL query to find the names of sailors who reserved all non-blue boa 8. Write a SQL query to find the name of the boat that is most popular one. 9. What does the following two queries do? SELECT sid SELECT sid FROM s WHERE rating > all ( SELECT rating FROM s s2 FROM s WHERE rating> any ( SELECT rating FROM s s2 WHERE s2.sname='Bob’)) WHERE s2.sname='Bob’)
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
Related questions
Question
Transcribed Image Text:### Question 3: SQL Queries
Considering the schema in Question 2:
- **Sailors**(sid: `integer`, sname: `string`, rating: `integer`, age: `real`);
- **Boats**(bid: `integer`, bname: `string`, color: `string`);
- **Reserves**(sid: `integer`, bid: `integer`, day: `date`);
#### Queries:
1. Write a SQL query to solve Question-2-1 (the first sub-question, please use a nested query).
2. Write a SQL query to solve Question-2-2 (the second sub-question).
3. Write a SQL query to solve Question-2-3 (the third sub-question).
4. Write a SQL query to find the name of oldest sailors for each rating level.
5. Find the average age of sailors for each rating level that has at least two sailors.
6. Write a SQL query to find the average number of boats reserved by different sailors.
7. Write a SQL query to find the names of sailors who reserved all non-blue boats.
8. Write a SQL query to find the name of the boat that is the most popular one.
9. What do the following two queries do?
```sql
SELECT sid
FROM s
WHERE rating > all (
SELECT rating
FROM s s2
WHERE s2.sname='Bob'
)
SELECT sid
FROM s
WHERE rating > any (
SELECT rating
FROM s s2
WHERE s2.sname='Bob'
)
```
#### Explanation of Queries:
1. **Nested Queries:** Writing nested queries involves using a subquery within another SQL query. In this context, nested queries help in finding specific sailors based on certain conditions from the schema provided.
2. **Finding Oldest Sailors:** This involves aggregations and grouping by different rating levels to identify the oldest sailor(s) in each group.
3. **Average Age Calculation:** This requires grouping by rating and having a condition to check if there are at least two sailors in each rating group, followed by calculating the average age.
4. **Reservations Analysis:** Calculating the average number of boats reserved by different sailors can involve counting reservations grouped by sailors and averaging them.
5. **Conditional Queries:** Identifying sailors who reserved all non-blue boats implicates conditional checks against the boat
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