I have an Oracle query, which has something to the effect of
Having Count(field) > (Long SQL statement that returns one row)
Both sides of the query work alone, but together I get a "not a group by" expression.
When replacing the long SQL statement with a number it works, but I assumed the two were equivalent if only one row is returned?
Edit
After doing some playing around I realized:
... Table T ... Having Count(field) > (Long SQL statement with Table A Where A.field = T.field)
It works when I replace T.field with any of the specific options for T.field, but when I reference T.field specifically I get the same "not a group by expression"
When Oracle parses your query it doesn't know if the query is going to return only one row or a bunch of rows. So simply append group by your_column to the end of your query.
For example this query returns one row:
select count(*) from user_objects;
But if I wanted to include sysdate along with that, I would have to do
select
sysdate the_date,
count(*)
from
user_objects
group by
the_date;
SELECT ...
FROM Table T ...
GROUP BY T.afield
HAVING Count(T.anotherfield)
> (Long SQL statement with Table A Where A.somefield = T.afield)
should work ok.
SELECT ...
FROM Table T ...
GROUP BY T.anotherfield
HAVING Count(T.anotherfield)
> (Long SQL statement with Table A WHERE A.somefield = T.afield)
should not work. A field (like T.afield) that is not included in the GROUP BY list, cannot be referenced in SELECT, HAVING or ORDER BY clauses. Only aggregate functions of that field can be referenced - you could have WHERE A.somefield = MIN(T.afield) for example.
Related
Can you filter a SQL table based on an aggregated value, but still show column values that weren't in the aggregate statement?
My table has only 3 columns: "Composer_Tune", "_Year", and "_Rank".
I want to use SQL to find which "Composer_Tune" values are repeated in each annual list, as well as which ranks the duplicated items had.
Since I am grouping by "Composer_Tune" & "Year", I can't list "_Rank" with my current code.
The image shows the results of my original "find the duplicates" query vs what I want:
Current vs Desired Results
I tried applying the concepts in this Aggregate Subquery StackOverflow post but am still getting "_Rank is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause" from this code:
WITH DUPE_DB AS (SELECT * FROM DB.dbo.[NAME] GROUP BY Composer_Tune, _Year HAVING COUNT(*)>1)
SELECT Composer_Tune, _Year, _Rank
FROM DUPE_DB
You need to explicitly declare the columns used in the Group By expression in the select columns.
You can use the following documentation if you are using transact sql for the proper use of Group By.
Simply join the aggregated resultset to original unit level table:
WITH DUPE_DB AS (
SELECT Composer_Tune, _Year
FROM DB.dbo.[NAME]
GROUP BY Composer_Tune, _Year
HAVING COUNT(*) > 1
)
SELECT n.Composer_Tune, n._Year, n._Rank
FROM DB.dbo.[NAME] n
INNER JOIN DUPE_DB
ON n.Compuser_Tune = DUPE_DB.Composer_Tune
AND n._Year = DUPE_DB._Year
ORDER n.Composer_Tune, n._Year
As we all know, the ORDER BY clause is processed after the SELECT clause, so a column alias in the SELECT clause can be used.
However, I find that I can’t use the aliased column in a calculation in the ORDER BY clause.
WITH data AS(
SELECT *
FROM (VALUES
('apple'),
('banana'),
('cherry'),
('date')
) AS x(item)
)
SELECT item AS s
FROM data
-- ORDER BY s; -- OK
-- ORDER BY item + ''; -- OK
ORDER BY s + ''; -- Fails
I know there are alternative ways of doing this particular query, and I know that this is a trivial calculation, but I’m interested in why the column alias doesn’t work when in a calculation.
I have tested in PostgreSQL, MariaDB, SQLite and Oracle, and it works as expected. SQL Server appears to be the odd one out.
The documentation clearly states that:
The column names referenced in the ORDER BY clause must correspond to
either a column or column alias in the select list or to a column
defined in a table specified in the FROM clause without any
ambiguities. If the ORDER BY clause references a column alias from
the select list, the column alias must be used standalone, and not as
a part of some expression in ORDER BY clause:
Technically speaking, your query should work since order by clause is logically evaluated after select clause and it should have access to all expressions declared in select clause. But without looking at having access to the SQL specs I cannot comment whether it is a limitation of SQL Server or the other RDBMS implementing it as a bonus feature.
Anyway, you can use CROSS APPLY as a trick.... it is part of FROM clause so the expressions should be available in all subsequent clauses:
SELECT item
FROM t
CROSS APPLY (SELECT item + '') AS CA(item_for_sort)
ORDER BY item_for_sort
It is simply due to the way expressions are evaluated. A more illustrative example:
;WITH data AS
(
SELECT * FROM (VALUES('apple'),('banana')) AS sq(item)
)
SELECT item AS s
FROM data
ORDER BY CASE WHEN 1 = 1 THEN s END;
This returns the same Invalid column name error. The CASE expression (and the concatenation of s + '' in the simpler case) is evaluated before the alias in the select list is resolved.
One workaround for your simpler case is to append the empty string in the select list:
SELECT
item + '' AS s
...
ORDER BY s;
There are more complex ways, like using a derived table or CTE:
;WITH data AS
(
SELECT * FROM (VALUES('apple'),('banana') AS sq(item)
),
step2 AS
(
SELECT item AS s FROM data
)
SELECT s FROM step2 ORDER BY s+'';
This is just the way that SQL Server works, and I think you could say "well SQL Server is bad because of this" but SQL Server could also say "what the heck is this use case?" :-)
I'm trying to compare two tables in a DB2 database in z/OS using SPUFI to submit SQL queries.
I'm doing this by using EXCEPT to see the difference between two SELECT queries.
I need to filter the SELECT statement from the first query with a WHERE clause.
SELECT KEY_FIELD_1,LOOKUP_FIELD_1
FROM TABLE_1
WHERE FILTER_FIELD = '1'
EXCEPT
SELECT KEY FIELD_2,LOOKUP_FIELD_2
FROM TABLE_2
I got results back, but it also returned an error -199 Is this because the WHERE clause is not present in the second SELECT statement?
ERROR: ILLEGAL USE OF KEYWORD EXCEPT.
TOKEN <ERR_STMT> <WNG_STMT> GET SQL
SAVEPOINT HOLD FREE ASSOCIATE WAS EXPECTED
Try introducing parentheses e.g.
( SELECT KEY_FIELD_1,LOOKUP_FIELD_1
FROM TABLE_1
WHERE FILTER_FIELD = '1' )
EXCEPT
( SELECT KEY FIELD_2,LOOKUP_FIELD_2
FROM TABLE_2 )
I'm running a pretty straightforward query using the database/sql and lib/pq (postgres) packages and I want to toss the results of some of the fields into a slice, but I need to know how big to make the slice.
The only solution I can find is to do another query that is just SELECT COUNT(*) FROM tableName;.
Is there a way to both get the result of the query AND the count of returned rows in one query?
Conceptually, the problem is that the database cursor may not be enumerated to the end so the database does not really know how many records you will get before you actually read all of them. The only way to count (in general case) is to go through all the records in the resultset.
But practically, you can enforce it to do so by using subqueries like
select *, (select count(*) from table) from table
and just ignore the second column for records other than first. But it is very rude and I do not recommend doing so.
Not sure if this is what you are asking for but you can call the ##Rowcount function to return the count of the previous select statement that has been executed.
SELECT mytable.mycol FROM mytable WHERE mytable.foo = 'bar'
SELECT ##Rowcount
If you want the row count included in your result set you can use the the OVER clause (MSDN)
SELECT mytable.mycol, count(*) OVER(PARTITION BY mytable.foo) AS 'Count' FROM mytable WHERE mytable.foo = 'bar'
You could also perhaps just separate two SQL statements with the a ; . This would return a result set of both statements executed.
You would used count(*)
SELECT count(distinct last)
FROM (XYZTable)
WHERE date(FROM_UNIXTIME(time)) >= '2013-10-28' AND
id = 90 ;
Could someone please explain to me why the following query is invalid? I'm running this query against an Oracle 10g database.
select count(test.*) from my_table test;
I get the following error: ORA-01747: invalid user.table.column, table.column, or column specification
however, the following two queries are valid.
select count(test.column) from my_table test;
select test.* from my_table test;
COUNT(expression) will count all rows where expression is not null. COUNT(*) is an exception, it returns the number of rows: * is not an alias for my_table.*.
As far as I know, Count(Table.*) is not officially supported in the SQL specification. Only Count(*) (count all rows returned) and Count(Table.ColumnName) (count all non-null values in the given column). So, even if the DBMS supported it, I would recommend against using it.`
This syntax only works in PostgreSQL and only because it has a record datatype (for which test.* is a meaningful expression).
Just use COUNT(*).
This query:
select count(test.column) from my_table test;
will return you the number of records for which test.column is not NULL.
This query:
select test.* from my_table test;
will just return you all records from my_table.
COUNT as such is probably the only aggregate that makes sense without parameters, and using an expression like COUNT(*) is just a way to call a function without providing any actual parameters to it.
You might reasonably want to find the number of records where test.column is not NULL if you are doing an outer join. As every table should have a PK (which is not null) you should be able to count the rows like that if you want:
select count(y.pk)
from x
left outer join y on y.pk = x.ck
COUNT(*) is no good here because the outer join is creating a null row for the table that is deficient in information.