%sAn expression was expected

Error Message:
Msg 2224, Level 16, State 1, Line 4
%sAn expression was expected

Severity level:
16.

Description:
This error message appears when an XQuery expression was expected, but not found.

Consequences:
The T-SQL statement can be parsed, but causes the error at runtime.

Resolution:
Errors of the Severity level 16 are generated by the user and are corrigible by the user. The statement cannot be run this way. If an XQuery expression is expected it has to be supplied in the expected manner.

Versions:
This error message was introduced with SQL Server 2005.

Example(s):
DECLARE @xml xml;
SET @xml = '<Result />';
SELECT
    @xml.query('for $a in(1, 2), $b in(3, 4,)
    where
        $a < $b
    return sum($a + $b)') as XML;

Remarks:
In the above example we try to add a comma to the second in clause without adding a valid XQuery expression after that comma. This raises the error.