I'm building an Access query with a LEFT JOIN that, among other things, counts the number of unique sampleIDs present in the left table of the JOIN, and counts the aggregate number of specimens (bugs) present in the right table of the JOIN, both for a given group of samples (TripID). Here's the pertinent chunk of SQL code:
SELECT DISTINCT t1.TripID, COUNT(t1.SampleID) AS Samples, SUM(t2.C1 + t2.C2)
AS Bugs FROM tbl_Sample AS t1
LEFT JOIN tbl_Bugs AS t2 ON t1.SampleID = t2.SampleID
GROUP BY t1.TripID
The trouble I'm having is that COUNT(t1.SampleID) is not giving me my desired result. My desired result is the number of unique SampleIDs present in t1 for a given TripID (let's say 7). Instead, what I get seems to be the number of rows in t2 for which the SampleID is contained within the given TripID group (let's say 77). How can I change this SQL query to get the desired number (7, not 77)?
just take the aggregate sum first on t2, then join with t2 like this:
SELECT t1.TripID, COUNT(t1.SampleID) AS Samples, SUM(t3.Bugs) as Bugs
FROM tbl_Sample AS t1
LEFT Join (
SELECT t2.SampleID, SUM(t2.C1 + t2.C2) as Bugs
FROM tbl_Bugs as t2
GROUP BY SampleID) AS t3 ON t1.SampleID = t3.SampleID
GROUP BY t1.TripID
This is a tricky query, because you have different hierarchies. Here is one method:
select s.tripid, count(*) as numsamples,
(select sum(b2.c1 + b2.c2)
from bugs b join
tbl_sample s2
on s2.sampleid = b.sampleid
where s2.tripid = s.tripid
) as numbugs
from tbl_sample s
group by s.tripid
You included a DISTINCT with a Group By. This is removing duplicates twice, which is unnecessarily complex. You can get rid of the DISTINCT.
I would have the count separate from what is going on in the group by.
SELECT dT.TripID
,(SELECT COUNT(DISTINCT(SampleID))
FROM Bugs B
WHERE B.TripID = dT.TripID
) AS [Samples]
,dT.Bugs
FROM (
SELECT t1.TripID
,SUM(t2.C1 + t2.C2) AS Bugs
FROM tbl_Sample AS t1
LEFT JOIN tbl_Bugs AS t2 ON t1.SampleID = t2.SampleID
GROUP BY t1.TripID
) AS dT
Related
I am sure I must be missing something obvious. I am trying to line up two tables with different measurement data for analysis, and my counts are coming back enormously high when I join the two tables together.
Here are the correct counts from my table1
select line_item_id,sum(is_imp) as imps
from table1
where line_item_id=5993252
group by 1;
Here are the correct counts from table2
select cs_line_item_id,sum(grossImpressions) as cs_imps
from table2
where cs_line_item_id=5993252
group by 1;
When I join the tables together, my counts become inaccurate:
select a.line_item_id,sum(a.is_imp) as imps,sum(c.grossImpressions) as cs_imps
from table1 a join table2 c
ON a.line_item_id=c.cs_line_item_id
where a.line_item_id=5993252
group by 1;
I'm using aggregates, group by, filtering, so I'm not sure where I'm going wrong. Here is the schema for these tables:
select a.*, b.imps table2_imps from
(select line_item_id,sum(is_imp) as imps
from table1
group by 1)a
join
(select line_item_id,sum(is_imp) as imps
from table1
group by 1)b
on a.select line_item_id=b.select line_item_id
You are generating a Cartesian product for each line_item_id. There are two relatively simply ways to solve this, one with a full join, the other with union all:
select line_item_id, sum(imps) as imps, sum(grossImpressions) as cs_imps
from ((select a.line_time_id, sum(is_imp) as imps, 0 as grossImpressions
from table1 a
where a.line_item_id = 5993252
group by a.line_item_id
) union all
(select c.line_time_id, 0 as imps, sum(grossImpressions) as grossImpressions
from table2 c
where c.line_item_id = 5993252
group by c.line_item_id
)
) ac
group by line_item_id;
You can remove the where clause from the subqueries to get the total for all line_tiem_ids. Note that this works even when one or the other table has no matching rows for a given line_item_id.
For performance, you really want to do the filtering before the group by.
Below is my insert query.
INSERT INTO /*+ APPEND*/ TEMP_CUSTPARAM(CUSTNO, RATING)
SELECT DISTINCT Q.CUSTNO, NVL(((NVL(P.RATING,0) * '10.0')/100),0) AS RATING
FROM TB_ACCOUNTS Q LEFT JOIN TB_CUSTPARAM P
ON P.TEXT_PARAM IN (SELECT DISTINCT PRDCD FROM TB_ACCOUNTS)
AND P.TABLENAME='TB_ACCOUNTS' AND P.COLUMNNAME='PRDCD';
In the previous version of the query, P.TEXT_PARAM=Q.PRDCD but during insert to TEMP_CUSTPARAM due to violation of unique constraint on CUSTNO.
The insert query is taking ages to complete. Would like to know how to use distinct with LEFT JOIN statement.
Thanks.
SELECT T1.Col1, T2.Col2 FROM Table1 T1
Left JOIN
(SELECT Distinct Col1, Col2 FROM Table2
) T2 ON T2.Id = T1.Id
You are missing criteria to join TB_ACCOUNTS records with their related TB_ACCOUNTS/PRDCD TB_CUSTPARAM records and thus cross join them instead. I guess you want:
INSERT INTO /*+ APPEND*/ TEMP_CUSTPARAM(CUSTNO, RATING)
SELECT DISTINCT
Q.CUSTNO,
NVL(P.RATING, 0) * 0.1 AS RATING
FROM TB_ACCOUNTS Q
LEFT JOIN TB_CUSTPARAM P ON P.TEXT_PARAM = Q.PRDCD
AND P.TABLENAME = 'TB_ACCOUNTS'
AND P.COLUMNNAME = 'PRDCD';
If the query is taking ages to complete, check first the execution plan. You may find some hints here - If you see a cartesian join on two non-trivial tables, probably the query should be revisited.
Than ask yourself what is the expectation of the query.
Do you expect one record per CUSTNO? Or can a customer have more than one rating?
One reting per customer could have sense from the point of business. To get unique customer list with rating
1) first get a UNIQUE CUSTNO - note that this is in generel not done with a DISTINCT clause, but if tehre are more rows per customer with a filter predicate, e.g. selecting the most recent row.
2) than join to the rating table
Suppose I have three tables in PostgreSQL:
table1 - id1, a_id, updated_by_id
table2 - id2, a_id, updated_by_id
Users - id, display_name
Suppose I am using the using the following query:
select count(t1.id1) from table1 t1
left join table2 t2 on (t1.a_id=t2.a_id)
full outer join users u1 t1.updated_by_id=u1.id)
full outer join users u2 t2.updated_by_id=u2.id)
where u1.id=100;
I get 50 as count.
Whereas with:
select count(t1.id1) from table1 t1
left join table2 t2 on (t1.a_id=t2.a_id)
full outer join users u1 t1.updated_by_id=u1.id)
full outer join users u2 t2.updated_by_id=u2.id)
where u2.id=100;
I get only 25 as count.
What is my mistake in the second query? What can I do to get the same count?
My requirement is that there is a single user table, referenced by multiple tables. I want to take the complete list of users and get the count of ids from different tables.
But the table on which I have joined alone returns the proper count but rest of them don't return the proper count. Can anybody suggest a way to modify my second query to get the proper count?
To simplify your logic, aggregate first, join later.
Guessing missing details, this query would give you the exact count, how many times each user was referenced in table1 and table2 respectively for all users:
SELECT *
FROM users u
LEFT JOIN (
SELECT updated_by_id AS id, count(*) AS t1_ct
FROM table1
GROUP BY 1
) t1 USING (id)
LEFT JOIN (
SELECT updated_by_id AS id, count(*) AS t2_ct
FROM table2
GROUP BY 1
) t2 USING (id);
In particular, avoid multiple 1-n relationships multiplying each other when joined together:
Two SQL LEFT JOINS produce incorrect result
To retrieve a single or few users only, LATERAL joins will be faster (Postgres 9.3+):
SELECT *
FROM users u
LEFT JOIN LATERAL (
SELECT count(*) AS t1_ct
FROM table1
WHERE updated_by_id = u.id
) ON true
LEFT JOIN LATERAL (
SELECT count(*) AS t2_ct
FROM table2
WHERE updated_by_id = u.id
) ON true
WHERE u.id = 100;
What is the difference between LATERAL JOIN and a subquery in PostgreSQL?
Explain perceived difference
The particular mismatch you report is due to the specifics of a FULL OUTER JOIN:
First, an inner join is performed. Then, for each row in T1 that does
not satisfy the join condition with any row in T2, a joined row is
added with null values in columns of T2. Also, for each row of T2 that
does not satisfy the join condition with any row in T1, a joined row
with null values in the columns of T1 is added.
So you get NULL values appended on the respective other side for missing matches. count() does not count NULL values. So you can get a different result depending on whether you filter on u1.id=100 or u2.id=100.
This is just to explain, you don't need a FULL JOIN here. Use the presented alternatives instead.
I can't to understand firebird group logic
Query:
SELECT t.id FROM T1 t
INNER JOIN T2 j ON j.id = t.jid
WHERE t.id = 1
GROUP BY t.id
works perfectly
But when I try to get other fields:
SELECT * FROM T1 t
INNER JOIN T2 j ON j.id = t.jid
WHERE t.id = 1
GROUP BY t.id
I get error: Invalid expression in the select list (not contained in either an aggregate function or the GROUP BY clause)
When you use GROUP BY in your query, the field or fields specified are used as 'keys', and data rows are grouped based on unique combinations of those 2 fields. In the result set, every such unique combination has one and only one row.
In your case, the only identifier in the group is t.id. Now consider that you have 2 records in the table, both with t.id = 1, but having different values for another column, say, t.name. If you try to select both id and name columns, it directly contradicts the constraint that one group can have only one row. That is why you cannot select any field apart from the group key.
For aggregate functions it is different. That is because, when you sum or count values or get the maximum, you are basically performing that operation only based on the id field, effectively ignoring the data in the other columns. So, there is no issue because there can only be one answer to, say, count of all names with a particular id.
In conclusion, if you want to show a column in the results, you need to group by it. This will however, make the grouping more granular, which may not be desirable. In that case, you can do something like this:
select * from T1 t
where t.id in
(SELECT t.id FROM T1 t
INNER JOIN T2 j ON j.id = t.jid
WHERE t.id = 1
GROUP BY t.id)
When you using GROUP BY clause in SELECT you should use only aggreagted functions or columns that listed in GROUP BY clause. More about GROUP BY clause:http://www.firebirdsql.org/manual/nullguide-aggrfunc.html
As example:
SELECT Max(t.jid), t.id FROM T1 t
INNER JOIN T2 j ON j.id = t.jid
WHERE t.id = 1
GROUP BY t.id
SELECT * FROM T1 t
INNER JOIN T2 j ON j.id = t.jid
WHERE t.id = 1
GROUP BY t.id
This will not execute,cause you have used t.id in group by, So all your columns in select clause should be using aggregate function , else those should be included in group by clause.
Select * means you are selecting all columns, so all columns except t.id are neither in group by nor in aggregate function.
Try this link, How to use GROUP BY in firebird
I have no idea if that title conveys what I want it to.
I have two tables containing phone records (one for each account) and I'd like to get call counts for the numbers that are common to each account. In other words:
Table 1
Number ...
8675309
8675309
8675310
8675310
8675312
Table 2
Number ...
8675309
8675309
8675309
8675310
8675311
Querying with something like:
SELECT DISTINCT table1.number, COUNT(table1.number), COUNT(table2.number) FROM table1, table2 WHERE table1.number = table2.number GROUP BY table1.number
would hopefully produce:
8675309|2|3
8675310|2|1
Instead, it currently produces something like:
8675309|6|6
8675310|2|2
It appears to be multiplying the count from each table. Presumably, this is because I'm not joining the tables the way I should for this goal. Or because by the time I ask for COUNT(table1.number) the tables have already been joined in some multiplicative way. Should I not be doing a JOIN and instead something that would read like: "where table2.number CONTAINS(table1.number)"?
Any tips?
One way is with subqueries:
SELECT t1.number, t1.table1Count, t2.table2Count
from (select number, count(*) table1Count
from table1
group by number) t1
inner join (select number, count(*) table2Count
from table2
group by number) t2
on t2.number = t1.number
This assumes that you only want to list numbers that appear in both tables. If you want to list all numbers that appear in one table and optionally the other, you'd use a left or right outer join; if you wanted all numbers that appeared in either or both tables, you'd use a full outer join.
Another and potentially more efficient way requires the presence of a single column that uniquely identifies each row in each table:
SELECT
t1.number
,count(distinct t1.PrimaryKeyValue) table1Count
,count(distinct t2.PrimaryKeyValue) table2Count
from table1 t1
inner join table2 t2
on t2.number = t1.number
group by t1.number
This makes the same assumptions as before, and can also be adjusted modified via outer joins.
One way is to use a couple of derived tables to compute your counts separately and then join them to produce your final summary:
select t1.number, t1.count1, t2.count2
from (select number, count(number) as count1 from table1 group by number) as t1
join (select number, count(number) as count2 from table2 group by number) as t2
on t1.number = t2.number
There are probably other ways but that should work and it is the first thing that came to mind.
You're getting your "multiplicative" effect pretty much for the reasons you suspect. If you have this:
table1(id,x) table2(id,x)
------------ ------------
1, a 4, a
2, a 5, a
3, b 6, b
Then joining them on x will give you this:
1,a, 4,a
1,a, 5,a
2,a, 4,a
2,a, 5,a
...
Usually you could use a GROUP BY to sort out the duplicates but you can't do that because it would mess up your per-table counts.
Try this:
select tab1.number,tab1.num1,tab2.num2
from
(SELECT number, COUNT(number) as num1 from table1 group by number) as tab1
left join
(SELECT number, COUNT(number) as num2 from table2 group by number) as tab2
on tab1.number = tab2.number