Understanding and Resolving ORA-00979 in SQL Queries
The ORA-00979 error, "not a GROUP BY expression," arises when a SQL query uses a GROUP BY
clause incorrectly. This happens when the SELECT
statement includes columns not mentioned in the GROUP BY
clause, or uses aggregate functions on columns without grouping.
The GROUP BY
clause groups rows with identical values in specified columns, allowing for aggregate functions (like SUM
, AVG
, MIN
, MAX
, COUNT
) to summarize data within each group. Without proper grouping, the database cannot determine which values to associate with each group, leading to the error.
Example and Solution:
A common scenario causing this error involves selecting multiple columns, but only grouping by a subset. The database is unable to determine a single value for the ungrouped columns within each group.
To fix this, either:
-
Include all non-aggregated columns in the
GROUP BY
clause: This is the simplest solution if you want to see all unique combinations of the selected columns. -
Use aggregate functions on non-grouped columns: If you only need summary statistics for certain columns, apply aggregate functions (like
MIN
,MAX
, orAVG
) to those columns. This will reduce the output to a single row per group.
Let's illustrate with a corrected query:
SELECT cr.review_sk, cr.cs_sk, cr.full_name, MIN(TO_CHAR(cf.fact_date, 'mm/dd/yyyy')) AS appt, -- Using MIN to aggregate the date cs.cs_id, cr.tracking_number FROM review cr, cs, fact cf WHERE cr.cs_sk = cs.cs_sk AND UPPER(cs.cs_id) LIKE '%' || UPPER(i_cs_id) || '%' AND row_delete_date_time IS NULL AND cr.review_sk = cf.review_wk (+) AND cr.fact_type_code (+) = 183050 GROUP BY cr.review_sk, cr.cs_sk, cr.full_name, cs.cs_id, cr.tracking_number -- All non-aggregated columns are now included ORDER BY cs.cs_id, cr.full_name;
By correctly including all non-aggregated columns in the GROUP BY
clause, the query will execute without the ORA-00979 error, ensuring data integrity and providing the expected results. Remember to choose the approach (including all columns or using aggregate functions) that best suits your data analysis needs.
The above is the detailed content of How to Resolve ORA-00979: Grouping Columns in SQL Queries?. For more information, please follow other related articles on the PHP Chinese website!

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