Spark2.0-error occurs when execute the sql statement which includes "nvl" function while spark1.6 supports

Spark2.0-error occurs when execute the sql statement which includes "nvl" function while spark1.6 supports

Error: org.apache.spark.sql.AnalysisException: cannot resolve 'nvl(b.`new_user`, 0)' due to data type mismatch: input to function coalesce should all be the same type, but it's [string, int]; line 2 pos 73 (state=,code=0)