Oracle-SQL-group by-error: not a single-component group Function

Error: not a single-component group Function

Example: Select deptno, count (empno) from EMP;

Error: not a single-component group Function

Cause:

1,If the grouping function is used in the program, you can use the following two cases:

Program existsGroupAnd specify the grouping conditions so that the grouping conditions can be queried together.

Changed:Select deptno, count (empno) from EMP group by deptno;

If you do not use grouping functions, you can only use grouping functions separately.

Changed:Select count (empno) from EMP;

 

2,When using grouping functions, fields other than grouping conditions cannot appear.

Summary: The fields selected in the SELECT statement to be queried must appear in the group by clause, except for the grouping function parameters.