错误：-无效的长度参数传递给LEFT或SUBSTRING函数

Question

SELECT TOP 20
total_worker_time/execution_count AS Avg_CPU_Time
,Execution_count
,total_elapsed_time/execution_count as AVG_Run_Time
,total_elapsed_time
,(SELECT
SUBSTRING(text,statement_start_offset/2+1,statement_end_offset
) FROM sys.dm_exec_sql_text(sql_handle)
) AS Query_Text
FROM sys.dm_exec_query_stats
ORDER BY Avg_CPU_Time DESC