SQL Server supports a subset of the XQuery language. One of features implemented within SQL Server XQuery are comparison operators. There are two kinds of comparison operators:
Operators for sequences comparison (=, !=, <, <=, >, >=) and
Operators for singletons comparison (named also scalar values; eq, ne, lt, le, gt, ge).
Two operators are available for equality comparison: = and eq .
First operator (=) can be used to compare sequences and / or singleton values / operands. Second operator (eq) can be used only with singleton values / operands. When two sequences are compared and both sequences have at least one common value the result is true, otherwise (there is no common value) the result is false.