Assign variable to the query results in Impala

I am trying to assign a value to a variable using single value result from a query but i keep getting syntax error . I am using HUE - Impala Editor 

Result of "Select distinct MonthEndSnapshotKey FROM vmge_1h_bmh_lynx_non_pu_sec.rundtcur" = 202005 with data type INT .

I want to assign it to variable Testvar 

SQL statements : 

SET $(testvar=Select distinct MonthEndSnapshotKey FROM vmge_1h_bmh_lynx_non_pu_sec.rundtcur};

select $(testvar}

• ParseException: Syntax error in line 1:undefined: SET $(testvar=Select distinct Mon... ^ Encountered: ( Expected: = CAUSED BY: Exception: Syntax error