ORA-00937: not a single-group group function

ORA-00937: not a single-group group function is one of the common messages we often get while aggregating data.

Causes of ORA-00937: not a single-group group function

This error happens when you are using a mixture of individual columns and aggregate functions in the same select statement without using any group by clause with that individual column

CREATE TABLE "EMP_DATA"
( "EMP_NO" NUMBER(4,0),
"EMP_NAME" VARCHAR2(10),
"JOB" VARCHAR2(9),
"MGR" NUMBER(4,0),
"HIREDATE" DATE,
"SALARY" NUMBER(7,2),
"COMM" NUMBER(7,2),
"DEPT_NO" NUMBER(2,0)
);
insert into emp_data values( 1000, 'BILL', 'MANAGER', 7839, to_date('1-5-2007','dd-mm-yyyy'), 2850, null, 10 );
insert into emp_data values( 1001, 'MATT', 'MANAGER', 7839, to_date('9-6-2008','dd-mm-yyyy'), 2450, null, 10 );
insert into emp_data values( 1002, 'SCOTT', 'ANALYST', 7566, to_date('9-6-2012','dd-mm-yyyy'), 3000, null, 20 );
insert into emp_data values( 1003, 'ARNOLD', 'ANALYST', 7566, to_date('9-6-2017','dd-mm-yyyy'), 3000, null, 20 );
insert into emp_data values( 1004, 'BANNER', 'ANALYST', 7567, to_date('9-7-2017','dd-mm-yyyy'), 4000, null, 20 );
insert into emp_data values( 1005, 'TOM', 'ANALYST', 7567, to_date('9-7-2017','dd-mm-yyyy'), 4000, null, 30 );
commit;

select dept_no,avg(salary) from emp_data;

select dept_no, avg(salary) from emp_data;
              *
Error at line 1
ORA-00937: not a single-group group function

Checklist to run to resolve ORA-00937: not a single-group group function

(1) Whenever we are using the Individual item and Group function in the same select statement, then we must include the group by clause with that individual column. So Right query for the above error will be

select dept_no,avg(salary) from emp_data group bp dept_no;

(2) we can also resolve this query, if we don’t want by dept_no wise, then this will also run correctly

select avg(salary) from emp_data ;

I hope you like these simple tips on ORA-00937: not a single-group group function

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