Tag: databases

To answer this question, you need to understand SQL (Structured Query Language) and the basic syntax used to extract data from a database.

The correct answer is A) SELECT.

Option A) SELECT - This option is correct because the SELECT statement is used to retrieve data from a database. It allows you to specify the columns you want to retrieve and the table(s) from which you want to retrieve the data. The SELECT statement is one of the fundamental statements in SQL and is used in almost every query.

Option B) GET - This option is incorrect because there is no GET statement in SQL for extracting data from a database. The GET statement is not a standard SQL statement.

Option C) OPEN - This option is incorrect because the OPEN statement is not used to extract data from a database. The OPEN statement is typically used to open a cursor in SQL, which is used to fetch rows from a result set.

Option D) EXTRACT - This option is incorrect because the EXTRACT statement is not used to extract data from a database. The EXTRACT statement is used to extract specific parts (such as year, month, day, etc.) from a date or time value in SQL.

Therefore, the correct answer is A) SELECT. This option is correct because the SELECT statement is used to extract data from a database.

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To select all the records from a table named "Persons" where the value of the column "FirstName" is "Peter", you can use the following SQL query:

B. SELECT * FROM Persons WHERE FirstName='Peter';

Explanation:

• The "SELECT" statement is used to retrieve data from a database table.
• The asterisk (*) is a wildcard character that represents all columns in the table.
• "FROM Persons" specifies the table name from which the data will be retrieved.
• "WHERE FirstName='Peter'" is the condition that filters the records to only those where the value of the "FirstName" column is "Peter".

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• Wrong explanation

To select all the records from a table named "Persons" where the value of the column "FirstName" starts with an "a," you can use the SQL query:

C. SELECT * FROM Persons WHERE FirstName LIKE 'a%';

Explanation:

Option A) SELECT * FROM Persons WHERE FirstName LIKE '%a'; This option is incorrect because the LIKE condition '%a' will match any FirstName that ends with 'a', not those that start with 'a'.

Option B) SELECT * FROM Persons WHERE FirstName='a'; This option is incorrect because it will only select records where the FirstName is exactly equal to 'a', not those that start with 'a'.

Option C) SELECT * FROM Persons WHERE FirstName LIKE 'a%'; This option is correct because the LIKE condition 'a%' will match any FirstName that starts with 'a'.

Option D) SELECT * FROM Persons WHERE FirstName='%a%'; This option is incorrect because the LIKE condition '%a%' will match any FirstName that contains 'a' anywhere in the string, not just at the beginning.

Therefore, the correct answer is C) SELECT * FROM Persons WHERE FirstName LIKE 'a%'.

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• Wrong explanation

To answer this question, you need to understand the syntax of the SQL SELECT statement and the ORDER BY clause.

The correct answer is B) SELECT * FROM Persons ORDER BY FirstName DESC;

Let's go through each option to understand why it is correct or incorrect:

Option A) SELECT * FROM Persons SORT 'FirstName' DESC; This option is incorrect because the correct keyword to use for sorting in SQL is ORDER BY, not SORT. Additionally, the column name should not be enclosed in single quotes.

Option B) SELECT * FROM Persons ORDER BY FirstName DESC; This option is correct because it uses the correct syntax for sorting records in descending order. The ORDER BY clause is used to sort the records based on the column specified (in this case, FirstName), and the DESC keyword is used to specify descending order.

Option C) SELECT * FROM Persons ORDER FirstName DESC; This option is incorrect because the ORDER keyword is missing before the column name. The correct syntax is ORDER BY.

Option D) SELECT * FROM Persons SORT BY 'FirstName' DESC; This option is incorrect because the correct keyword to use for sorting in SQL is ORDER BY, not SORT. Additionally, the column name should not be enclosed in single quotes.

The correct answer is B) SELECT * FROM Persons ORDER BY FirstName DESC. This option is correct because it uses the correct syntax for sorting records in descending order.

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• Wrong explanation