SQL Test on Functions

What does SQL stand for?

• Structured Query Language

• Simple Query Language

• Standard Question Language

• Structured Question Language

Answer explanation

SQL stands for Structured Query Language, which is the standard language used for managing and manipulating relational databases. The other options do not accurately describe SQL.

Which function is used to calculate the total number of rows in a table?

• SUM()

• COUNT()

• TOTAL()

• NUM()

Answer explanation

The COUNT() function is specifically designed to count the number of rows in a table. Unlike SUM(), TOTAL(), or NUM(), which serve different purposes, COUNT() directly provides the total row count.

What will the following query return? SELECT UPPER('hello');

• Hello

• hello

• HELLO

• hELLO

Answer explanation

The query SELECT UPPER('hello') converts the string 'hello' to uppercase. Therefore, it returns 'HELLO', which is the correct answer.

Which function is used to retrieve the current date in MySQL?

• GETDATE()

• CURRENT_DATE()

• NOW()

• TODAY()

Answer explanation

The function CURRENT_DATE() is used in MySQL to retrieve the current date. GETDATE() and NOW() are used in other SQL dialects, while TODAY() is not a valid MySQL function.

What does the ROUND() function do?

• Rounds a number to the nearest integer

• Rounds a number to a specified decimal place

• Both A and B

• None of the above

Answer explanation

The ROUND() function can round a number to the nearest integer or to a specified number of decimal places. Therefore, the correct answer is 'Both A and B'.

Which of the following functions can be used to find the length of a string in MySQL?

• SIZE()

• LENGTH()

• COUNT()

• CHAR_LENGTH()

Answer explanation

In MySQL, the LENGTH() function is used to find the length of a string in bytes. CHAR_LENGTH() can also be used to find the number of characters. SIZE() and COUNT() are not valid for this purpose.

What will SELECT NOW(); return?

• The current time

• The current date and time

• The current day

• The current year

Answer explanation

The SELECT NOW(); command in SQL returns the current date and time in the format 'YYYY-MM-DD HH:MM:SS'. Therefore, the correct answer is 'The current date and time'.

Which function is used to convert a string to lowercase?

• LOWER()

• LCASE()

• Both A and B

• LOWERCASE()

Answer explanation

The functions LOWER() and LCASE() are both used to convert a string to lowercase in different database systems. Therefore, the correct answer is 'Both A and B'.

What will SELECT SUBSTRING('Hello World', 1, 5); return?

• Hello

• Hello World

• ello

• World

Answer explanation

The function SELECT SUBSTRING('Hello World', 1, 5) extracts a substring starting from position 1 for 5 characters. Thus, it returns 'Hello', which is the correct answer.

What does the CONCAT() function do?

• Joins two or more strings

• Splits a string

• Changes the case of a string

• Counts characters in a string

Answer explanation

The CONCAT() function is used to join two or more strings together into a single string. This makes 'Joins two or more strings' the correct choice, while the other options describe different string operations.