SQLServerException：使用Groovy不支持从UNKNOWN到UNKNOWN的转换

Question

我正在尝试使用针对SQL Server数据库的Groovy SQL运行查询。但是，我收到以下异常：com.microsoft.sqlserver.jdbc.SQLServerException: The conversion from UNKNOWN to UNKNOWN is unsupported

Grails version: 2.2.5
SQL Server version: 9.0

我从Grails控制台运行的脚本：

import groovy.sql.*

Sql sql = Sql.newInstance(ctx.dataSource_sqlserver)

def query = '''
    select
        avg(cast(score as decimal)) average_score
    from
        StudentQuestionScores
    where
        id in ( :ids )
        and question = :question
'''

def ids = Student.list().collect { it.id }  // Succeeds
def row = sql.firstRow(query, [ids: ids, question: 'Insert Question Here']) // ERROR

sql.close()

println row.average_score // Never makes it here :(

有谁知道为什么会这样或我如何解决它？谢谢！

堆栈跟踪：

com.microsoft.sqlserver.jdbc.SQLServerException: The conversion from UNKNOWN to UNKNOWN is unsupported.
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:190)
    at com.microsoft.sqlserver.jdbc.DataTypes.throwConversionError(DataTypes.java:1117)
    at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.setObject(SQLServerPreparedStatement.java:991)
    at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.setObjectNoType(SQLServerPreparedStatement.java:926)
    at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.setObject(SQLServerPreparedStatement.java:935)
    at org.apache.commons.dbcp.DelegatingPreparedStatement.setObject(DelegatingPreparedStatement.java:169)
    at org.apache.commons.dbcp.DelegatingPreparedStatement.setObject(DelegatingPreparedStatement.java:169)
    at groovy.sql.Sql.setObject(Sql.java:3649)
    at groovy.sql.Sql.setParameters(Sql.java:3614)
    at groovy.sql.Sql.getPreparedStatement(Sql.java:3875)
    at groovy.sql.Sql.getPreparedStatement(Sql.java:3922)
    at groovy.sql.Sql.access$900(Sql.java:227)
    at groovy.sql.Sql$PreparedQueryCommand.runQuery(Sql.java:4078)
    at groovy.sql.Sql$AbstractQueryCommand.execute(Sql.java:4027)
    at groovy.sql.Sql.rows(Sql.java:1945)
    at groovy.sql.Sql.rows(Sql.java:1835)
    at groovy.sql.Sql.rows(Sql.java:1816)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)