什么是“相关标量子查询必须聚合"?意思是? [英] What does "Correlated scalar subqueries must be Aggregated" mean?

问题描述

我使用 Spark 2.0.

I use Spark 2.0.

我想执行以下 SQL 查询:

I'd like to execute the following SQL query:

val sqlText = """
select
  f.ID as TID,
  f.BldgID as TBldgID,
  f.LeaseID as TLeaseID,
  f.Period as TPeriod,
  coalesce(
    (select
       f ChargeAmt
     from
       Fact_CMCharges f
     where
       f.BldgID = Fact_CMCharges.BldgID
     limit 1),
     0) as TChargeAmt1,
  f.ChargeAmt as TChargeAmt2,
  l.EFFDATE as TBreakDate
from
  Fact_CMCharges f
join
  CMRECC l on l.BLDGID = f.BldgID and l.LEASID = f.LeaseID and l.INCCAT = f.IncomeCat and date_format(l.EFFDATE,'D')<>1 and f.Period=EFFDateInt(l.EFFDATE) 
where
  f.ActualProjected = 'Lease'
except(
  select * from TT1 t2 left semi join Fact_CMCharges f2 on t2.TID=f2.ID) 
"""
val query = spark.sql(sqlText)
query.show()

似乎coalesce中的内部语句给出了以下错误:

It seems that the inner statement in coalesce gives the following error:

pyspark.sql.utils.AnalysisException: u'Correlated scalar subqueries must be Aggregated: GlobalLimit 1
+- LocalLimit 1

查询有什么问题?

推荐答案

您必须确保您的子查询根据定义(而不是根据数据)只返回一行.否则 Spark Analyzer 在解析 SQL 语句时会报错.

You have to make sure that your sub-query by definition (and not by data) only returns a single row. Otherwise Spark Analyzer complains while parsing the SQL statement.

因此，当催化剂无法仅通过查看 SQL 语句(不查看您的数据)100% 确定子查询仅返回单行时，就会抛出此异常.

So when catalyst can't make 100% sure just by looking at the SQL statement (without looking at your data) that the sub-query only returns a single row, this exception is thrown.

如果您确定您的子查询只给出一行，您可以使用以下之一 聚合标准函数，让Spark Analyzer开心:

If you are sure that your subquery only gives a single row you can use one of the following aggregation standard functions, so Spark Analyzer is happy:

• 第一
• 平均值
• max
• min

这篇关于什么是“相关标量子查询必须聚合"?意思是?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！