Difference between revisions of "Incorrect GROUP BY"
From SQLZOO
(Created page with "<div class='err'> <div class=params>schema:gisq</div> <div class = "link e-oracle">ORA-00979: not a GROUP BY expression</div> <div class = "link e-mysql">ORA-00979: not a GROU...") |
|||
| Line 9: | Line 9: | ||
<div> | <div> | ||
| − | <h2>Problem</h2 | + | <h2>Problem</h2> |
<p>When using a GROUP BY clause every field in the SELECT list must be either: </p> | <p>When using a GROUP BY clause every field in the SELECT list must be either: </p> | ||
<ul> | <ul> | ||
Revision as of 11:47, 19 July 2012
schema:gisq
ORA-00979: not a GROUP BY expression
ORA-00979: not a GROUP BY expression
ORA-00979: not a GROUP BY expression
Error 7 ERROR: Attribute xxx.xxx must be GROUPed or used in an aggregate function
SQL0119N An expression starting with "xxx" specified in a SELECT clause, HAVING clause, or ORDER BY clause is not specified in the GROUP BY clause or it is in a SELECT clause, HAVING clause, or ORDER BY clause with a column function and no GROUP BY clause is specified. SQLSTATE=42803
Msg 8120 Column 'xxx' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause. (SQL-42000)
Problem
When using a GROUP BY clause every field in the SELECT list must be either:
- One of the GROUP BY terms - in this case region
- An aggregate function - for example SUM or COUNT
- An expression based on the above
In the example the field name may not be used on the SELECT line.
In a group by line each region shows up only once - however in a typical region such as Africa there are several different name values. WHich one should SQL pick?
Solutions
- Remove the offending field from the SELECT line
- Add the field to the GROUP BY clause
- Aggregate the offending field
SELECT name, region, MAX(population) FROM bbc GROUP BY region
