A SELECT list cannot include both a group function, such as AVG, COUNT, MAX, MIN, SUM, STDDEV, or VARIANCE, and an individual column expression, unless the individual column expression is included in a GROUP BY clause.
?
Drop either the group function or the individual column expression from the SELECT list or add a GROUP BY clause that includes all individual column expressions listed.
eg:
SQL> select owner, count(*)
? 2? from dba_segments;
select owner, count(*)
?????? *
ERROR at line 1:
ORA-00937: not a single-group group function
Because we have a group function (COUNT) in our column list, and an additional column (OWNER), we have to include the GROUP BY clause in our select statement.
SQL> select owner, count(*)
? 2? from dba_segments
? 3? group by owner;
OWNER??????????????????????????? COUNT(*)
------------------------------ ----------
USER1????????????????????????????? 166
USER2????????????????????????????? 166
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