1. Case-sensitive comparison: By default, most databases perform case-sensitive comparisons on VARCHAR values. This means that ‘apple’ and ‘Apple’ will be considered different values. To perform a case-insensitive comparison, you can use the appropriate case-insensitive collation or use an appropriate string manipulation function to convert the values to the same case before comparing.

Example:

SELECT * 
FROM my_table 
WHERE column1 = column2 COLLATE SQL_Latin1_General_CP1_CI_AS;

1. LIKE operator: The LIKE operator can be used to compare VARCHAR values using wildcard characters. It allows you to specify patterns to match against the values. The ‘%’ character represents any sequence of characters, and the ‘_’ character represents a single character.

Example:

SELECT * 
FROM my_table 
WHERE column LIKE 'abc%'; -- Returns rows where column starts with 'abc'

1. String functions: SQL provides various string functions that can be used to manipulate and compare VARCHAR values. These functions include SUBSTRING, UPPER, LOWER, and LENGTH, among others. These functions can be used to extract substrings, convert case, compute lengths, and perform other operations on VARCHAR values before comparing them.

Example:

SELECT * 
FROM my_table 
WHERE LENGTH(column1) > LENGTH(column2);

In conclusion, comparing VARCHAR values in SQL involves using comparison operators, collations for case-insensitive comparison, the LIKE operator for pattern matching, and string functions for manipulating and comparing values.