The result of this SQL in MySQL is
but it cannot be used in memsql
Maybe the version is too old
but after sign in, where is the memsql installation package download url ? I can’t find it 
Which version of memsql are you running?
select @@memsql_version
Thank you for your reply，It’s really a version problem,I switched to 5.6 version ，I have a new problem :Feature ‘REFERENTIAL ACTIONS’ is not supported by MemSQL. Must it be the latest version? But where is the latest version download?I can not find it. :汗:
Are you using memsql-ops or memsql tools to manage your cluster? Given the age of the cluster I assume memsql-ops? You can upgrade using ops via memsql-ops memsql-upgrade (see SingleStoreDB Cloud · SingleStore Documentation)
That said, even the latest version of memsql (7.1 as of the time of writing) doesn’t support foreign keys.
By the way，Does the latest version of memsql 7.1 support subselect？
Yes it does. It’s A LOT better. Check out the long list of improvements: SingleStoreDB Cloud · SingleStore Documentation
Correlated subselect that can not be transformed and does not match on shard keys
what does this mean？
Can you share the query you ran that hits that error?
