SSC IMD SA 2017 – Question 176

Which of the following statements is true?

• The basic data type char(n) is a fixed-length character string and varchar(n) is an equal-length character string
• The basic data type char(n) is a uniform-length character string and varchar(n) is a variable-length character string
• The basic data type char(n) is a fixed-length character string and varchar(n) is a variable-length character string
• The basic data type char(n) is a variable-length character string and varchar(n) is an equal-length character string

Detailed Explanation:

The correct answer is c) char(n) is a fixed-length character string and varchar(n) is a variable-length character string (मूल डेटा प्रकार char (n) एक निश्चित लंबाई कैरेक्टर स्ट्रिंग और varchar (n) चर लंबाई कैरेक्टर है।).

In Relational Database Management Systems (SQL standard), character string data types are defined as follows:

• CHAR(n) (Fixed-Length): Represents a fixed-length string of size $n$. If a string of fewer than $n$ characters is inserted, the RDBMS automatically right-pads the remaining space with blank characters (spaces) up to length $n$. Memory is pre-allocated uniformly.
• VARCHAR(n) (Variable-Length): Represents a variable-length string with a maximum capacity of $n$ characters. It allocates only the actual number of characters stored plus 1 or 2 prefix bytes used to record the string’s length, thus optimizing disk storage and memory usage.

Therefore, statement c accurately distinguishes fixed-length char(n) from variable-length varchar(n).