What does "Correlated scalar subqueries must be Aggregated" mean?
<p>I use Spark 2.0.</p>

<p>I'd like to execute the following SQL query:</p>

<pre><code>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')&lt;&gt;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()
</code></pre>

<p>It seems that the inner statement in <code>coalesce</code> gives the following error:</p>

<pre><code>pyspark.sql.utils.AnalysisException: u'Correlated scalar subqueries must be Aggregated: GlobalLimit 1\n+- LocalLimit 1\n
</code></pre>

<p>What's wrong with the query?</p>