Select The Correct Answer.Which Query Will Give The Following Result When It Is Applied To The Original Table?Result Table:$\[ \begin{array}{|l|c|} \hline \text{Name} & \text{Age} \\ \hline \text{Joe} & 24 \\ \text{Frank} & 20

Feb 27, 2025 by ADMIN 227 views

**Selecting the Correct Query for the Desired Result**

When working with databases, it's essential to understand how to write effective queries that produce the desired results. In this article, we'll explore how to select the correct query to achieve a specific outcome.

Understanding the Original Table

Before we dive into the queries, let's take a closer look at the original table.

Name	Age
Joe	24
Frank	20

The Desired Result Table

The result table we're aiming for is as follows:

Name	Age
Joe	24

Analyzing the Result Table

Upon examining the result table, we can see that it contains only one row, which is the row for "Joe" with an age of 24. This suggests that the query we're looking for is likely to filter the original table based on the name and age.

Query Options

There are several query options that could potentially produce the desired result. Let's explore a few possibilities:

Option 1: Filtering by Name

One possible query is to filter the original table by the name "Joe". This can be achieved using the following SQL query:

SELECT *
FROM original_table
WHERE name = 'Joe';

However, this query will only return the row for "Joe" if the name is exactly "Joe". If the name is stored in a case-insensitive manner, this query may not produce the desired result.

Option 2: Filtering by Age

Another possible query is to filter the original table by the age 24. This can be achieved using the following SQL query:

SELECT *
FROM original_table
WHERE age = 24;

This query will return all rows with an age of 24, regardless of the name.

Option 3: Combining Filters

To achieve the desired result, we can combine the filters for name and age. This can be achieved using the following SQL query:

SELECT *
FROM original_table
WHERE name = 'Joe' AND age = 24;

This query will return only the row for "Joe" with an age of 24.

Conclusion

In conclusion, the correct query to produce the desired result table is the one that combines filters for name and age. This query is as follows:

SELECT *
FROM original_table
WHERE name = 'Joe' AND age = 24;

This query will return only the row for "Joe" with an age of 24, which is the desired result.

Best Practices

When writing queries, it's essential to follow best practices to ensure that the query produces the desired result. Here are a few best practices to keep in mind:

Use meaningful table and column names: Using meaningful table and column names can make it easier to write and understand queries.
Use filters to narrow down the result set: Filters can be used to narrow down the result set and produce the desired result.
Combine filters to achieve the desired result: Combining filters can be used to achieve the desired result.

In this article, we'll address some of the most frequently asked questions related to selecting the correct query for the desired result.

Q: What is the difference between a filter and a query?

A: A filter is a condition that is applied to a query to narrow down the result set. A query is a statement that is used to retrieve data from a database.

Q: How do I write a query that filters by multiple conditions?

A: To write a query that filters by multiple conditions, you can use the AND operator to combine multiple conditions. For example:

SELECT *
FROM original_table
WHERE name = 'Joe' AND age = 24;

Q: What is the difference between a case-sensitive and case-insensitive query?

A: A case-sensitive query is one that treats uppercase and lowercase letters as distinct. A case-insensitive query is one that treats uppercase and lowercase letters as the same. For example:

SELECT *
FROM original_table
WHERE name = 'JOE';  // Case-sensitive query
SELECT *
FROM original_table
WHERE name = 'joe';  // Case-insensitive query

Q: How do I write a query that filters by a range of values?

A: To write a query that filters by a range of values, you can use the BETWEEN operator. For example:

SELECT *
FROM original_table
WHERE age BETWEEN 20 AND 30;

Q: What is the difference between a subquery and a join?

A: A subquery is a query that is nested inside another query. A join is a query that combines data from two or more tables based on a common column. For example:

SELECT *
FROM original_table
WHERE age IN (SELECT age FROM subquery);

SELECT *
FROM original_table
JOIN subquery ON original_table.age = subquery.age;

Q: How do I write a query that filters by a specific date range?

A: To write a query that filters by a specific date range, you can use the BETWEEN operator. For example:

SELECT *
FROM original_table
WHERE date BETWEEN '2020-01-01' AND '2020-12-31';

Q: What is the difference between a query that uses a WHERE clause and a query that uses a HAVING clause?

A: A query that uses a WHERE clause filters the result set based on a condition. A query that uses a HAVING clause filters the result set based on a condition that is applied to a grouped result set. For example:

SELECT *
FROM original_table
WHERE age > 20;

SELECT *
FROM original_table
GROUP BY age
HAVING COUNT(*) > 1;

Q: How do I write a query that filters by a specific column value?

A: To write a query that filters by a specific column value, you can use the WHERE clause. For example:

SELECT *
FROM original_table
WHERE name = 'Joe';

Q: What is the difference between a query that uses a SELECT statement and a query that uses a INSERT statement?

A: A query that uses a SELECT statement retrieves data from a database. A query that uses an INSERT statement adds new data to a database. For example:

SELECT *
FROM original_table;

INSERT INTO original_table (name, age)
VALUES ('Jane', 25);

Conclusion

In conclusion, writing effective queries requires a good understanding of the database schema, the data types, and the query language. By following best practices and using the correct query, you can produce the desired result table and achieve your goals.

Best Practices

When writing queries, it's essential to follow best practices to ensure that the query produces the desired result. Here are a few best practices to keep in mind:

Use meaningful table and column names: Using meaningful table and column names can make it easier to write and understand queries.
Use filters to narrow down the result set: Filters can be used to narrow down the result set and produce the desired result.
Combine filters to achieve the desired result: Combining filters can be used to achieve the desired result.
Use the correct data types: Using the correct data types can ensure that the query produces the desired result.
Test the query: Testing the query can help ensure that it produces the desired result.