Tag: databases

To select all the columns from a table named 'Persons' using SQL, the user needs to use the following query:

B. SELECT * FROM Persons

Option A is incorrect because the SQL keyword for selecting all columns is not 'all,' but rather '*'.

Option C is incorrect because the '*' should come before the table name, and not after it.

Option D is incorrect because 'Persons' alone does not specify which columns to select from the table.

Therefore, the correct answer is option B.

To select all the records from the table named 'Persons' where the value of the column 'FirstName' is 'Peter', the correct SQL query is:

D. SELECT * FROM Persons WHERE FirstName='Peter'

Let's go through each option and explain why the other options are incorrect:

A. SELECT * FROM Persons WHERE FirstName <> 'Peter' This query selects all records where the 'FirstName' column is not equal to 'Peter'. It is the opposite of what we want, so this option is incorrect.

B. SELECT [all] FROM Persons WHERE FirstName='Peter' The use of '[all]' is not necessary in this query. It should be replaced with '*' to select all columns. Additionally, the operator '=' should be used instead of 'LIKE' since we are looking for an exact match. Therefore, this option is incorrect.

C. SELECT [all] FROM Persons WHERE FirstName LIKE 'Peter' The 'LIKE' operator is used for pattern matching and allows the use of wildcards (% or _). Since we are looking for an exact match of 'Peter', the '=' operator should be used instead. Therefore, this option is incorrect.

D. SELECT * FROM Persons WHERE FirstName='Peter' This option correctly selects all records from the 'Persons' table where the 'FirstName' column is equal to 'Peter'.

So, the correct answer is: D. SELECT * FROM Persons WHERE FirstName='Peter'

To solve this question, the user needs to know SQL syntax and the concept of sorting query results in a descending order based on a specific column.

Now, let's go through each option and explain why it is right or wrong:

A. SELECT * FROM Persons ORDER FirstName DESC This option is incorrect because the correct syntax for sorting query results in SQL requires the use of the "ORDER BY" clause followed by the column name to sort by, and then the keyword "DESC" to specify descending order. Therefore, the correct syntax should be "ORDER BY FirstName DESC" instead of "ORDER FirstName DESC".

B. SELECT * FROM Persons ORDER BY FirstName DESC This option is correct. The "ORDER BY" clause is used to sort the query results based on a specific column. In this case, we want to sort the results in descending order based on the "FirstName" column. Therefore, the correct syntax is "ORDER BY FirstName DESC".

C. SELECT * FROM Persons SORT BY 'FirstName' DESC This option is incorrect because there is no "SORT" keyword in SQL. The correct keyword to use is "ORDER BY". Additionally, the column name should not be enclosed in single quotes. Therefore, the correct syntax should be "ORDER BY FirstName DESC" instead of "SORT BY 'FirstName' DESC".

D. SELECT * FROM Persons SORT 'FirstName' DESC This option is incorrect because the correct keyword to use for sorting query results in SQL is "ORDER BY" rather than "SORT". Additionally, the column name should not be enclosed in single quotes. Therefore, the correct syntax should be "ORDER BY FirstName DESC" instead of "SORT 'FirstName' DESC".

The Answer is: B