I have a access db that have this kind of data and I would like to write a query that will output the combined rows. I have looked into joins and other things but don't really grasp how they can do what I want.
Person Company Item1 Item2 Item3
1 A 5
2 A 3
3 A 4
4 B 3
5 B 2
6 B 1
Combine it to
Company Item1 Item2 Item3
A 5 3 4
B 3 2 1
It is supposed to be only one Item1 per Company and I realize there might be an issue if I have double. But that is another problem.
As you mentioned, there definitely could be issues if there are more of each item for a single company, but that could be more of a database design issue, so let's not go into that! :)
Totaling/summing the item values
If the numbers under "Item1", "Item2", "Item3", etc are meant to be totaled/summed together, then you have a nice easy query on your hands:
SELECT Company, Sum(Item1) AS Item1Total, Sum(Item2) AS Item2Total, Sum(Item3) AS Item3Total
FROM test
GROUP BY Company;
Finding the first non-NULL item value
If you need to find the first non-NULL value for each item, then your query is going to be a little bit more complex. This example uses sub-queries to find the first non-NULL entry for each item column/field for the current company:
SELECT t0.Company, (
SELECT TOP 1 t1.Item1
FROM test AS t1
WHERE t1.Company = t0.Company
AND t1.Item1 IS NOT NULL
) AS Item1Total, (
SELECT TOP 1 t2.Item2
FROM test AS t2
WHERE t2.Company = t0.Company
AND t2.Item2 IS NOT NULL
) AS Item2Total, (
SELECT TOP 1 t3.Item3
FROM test AS t3
WHERE t3.Company = t0.Company
AND t3.Item3 IS NOT NULL
) AS Item3Total
FROM test AS t0
GROUP BY Company;
Related
Hello everyone this is my first question here. I have been browsing thru the questions but couldnt quite find the answer to my problem:
I have a couple of tables which I need to join. The key I join with is non unique(in this case its a date). This is working fine but now I also need to group the results based on another column without getting cross-join like results (meaning each value of this column should only appear once but depending on the table used the column can have different values in each table)
Here is an example of what I have and what I would like to get:
Table1
Date/Key
Group Column
Example Value1
01-01-2022
a
1
01-01-2022
d
2
01-01-2022
e
3
01-01-2022
f
4
Table 2
Date/Key
Group Column
Example Value 2
01-01-2022
a
1
01-01-2022
b
2
01-01-2022
c
3
01-01-2022
d
4
Wanted Result :
Table Result
Date/Key
Group Column
Example Value1
Example Value2
01-01-2022
a
1
1
01-01-2022
b
NULL
2
01-01-2022
c
NULL
3
01-01-2022
d
2
4
01-01-2022
e
3
NULL
01-01-2022
f
4
NULL
I have tryed a couple of approaches but I always get results with values in group column appear multiple times. I am under the impression that full joining and then grouping over the group column shoul work but apparently I am missing something. I also figured I could bruteforce the result by left joining everything with setting the on to table1.date = table2.date AND table1.Groupcolumn = table2.Groupcolumn ect.. and then doing UNIONs of all permutations (so each table was on "the left" once) but this is not only tedious but bigquery doesnt like it since it contains too many sub queries.
I feel kinda bad that my first question is something that I should actually know but I hope someone can help me out!
I do not need a full code solution just a hint to the correct approach would suffice (also incase I missed it: if this was already answered I also appreciate just a link to it!)
Edit:
So one solution I came up with, which appears to work, was to select the group column of each table and union them as a with() and then join this "list" onto the first table like
list as(Select t1.GroupColumn FROM Table_1 t1 WHERE CONDITION1
UNION DISTINCT Select t1.GroupColumn FROM Table_1 t1 WHERE CONDITION2 ... ect)
result as (
SELECT l.GoupColumn, t1.Example_Value1, t2.Example_Value2
FROM Table_1 t1
LEFT JOIN( SELECT * FROM list) s
ON S.GroupColumn = t1.GroupColumn
LEFT JOIN Table_2 t2
on S.GroupColumn = t2.GroupColumn
and t1.key = t2.key
...
)
SELECT * FROM result
I think what you are looking for is a FULL OUTER JOIN and then you can coalesce the date and group columns. It doesn't exactly look like you need to group anything based on the example data you posted:
SELECT
coalesce(table1.date_key, table2.date_key) AS date_key,
coalesce(table1.group_column, table2.group_column) AS group_column,
table1.example_value_1,
table2.example_value_2
FROM
table1
FULL OUTER JOIN
table2
USING
(date_key,
group_column)
ORDER BY
date_key,
group_column;
Consider below simple approach
select * from (
select *, 'example_value1' type from table1 union all
select *, 'example_value2' type from table2
)
pivot (
any_value(example_value1)
for type in ('example_value1', 'example_value2')
)
if applied to sample data in your question - output is
I tried to solve one problem but without success.
I have two list of number
{1,2,3,4}
{5,6,7,8,9}
And I have table
ID Number
1 1
1 2
1 7
1 2
1 6
2 8
2 7
2 3
2 9
Now I need to count how many times number from second list come after number from first list but I should count only one by one id
in example table above result should be 2
three matched pars but because we have only two different IDs result is 2 instead 3
Pars:
1 2
1 7
1 2
1 6
2 3
2 9
note. I work with MSSQL
Edit. There is one more column Date which determined order
Edit2 - Solution
i write this query
SELECT * FROM table t
left JOIN table tt ON tt.ID = t.ID
AND tt.Date > t.Date
AND t.Number IN (1,2,3,4)
AND tt.Number IN (6,7,8,9)
And after this I had a plan to group by id and use only one match for each id but execution take a lot time
Here is a query that would do it:
select a.id, min(a.number) as a, min(b.number) as b
from mytable a
inner join mytable b
on a.id = b.id
and a.date < b.date
and b.number in (5,6,7,8,9)
where a.number in (1,2,3,4)
group by a.id
Output is:
id a b
1 1 6
2 3 9
So the two pairs are output each on one line, with the value a belonging to the first group of numbers, and the value of column b to the second group.
Here is a fiddle
Comments on attempt (edit 2 to question)
Later you added a query attempt to your question. Some comments about that attempt:
You don't need a left join because you really want to have a match for both values. inner join has in general better performance, so use that.
The condition t.Number IN (1,2,3,4) does not belong in the on clause. In combination with a left join the result will include t records that violate this condition. It should be put in the where clause.
Your concern about performance may be warranted, but can be resolved by adding a useful index on your table, i.e. on (id, number, date) or (id, date, number)
I'm wondering if it was doable (in one query if possible) to make the query return a default value if a row is missing ? For example takes these 2 tables and given my query takes 2 parameter (place_id and user_id)
T1
place_id / tag_id
1 2
1 3
1 4
2 4
3 2
4 5
T2
user_id / tag_id / count
100 2 1
100 3 20
200 4 30
200 2 2
300 5 22
As you see, the pair user/tag (100,4) is missing. What I would like to archive is a query that will return me these 3 results
tag_id / count
2 1
3 20
4 0
I know that i can do this with something like this but it doesn't really match the final result as it only works if i know in advance the tag_id... and obviously only return 1 row..:
SELECT T1.tag_id, T2.count
from T1 t1
left join T2 t2 on t1.tagId=t2.tag_id
where t1.place_id=1
UNION ALL
select tag_id,0
from T1
where not exist (select 1 from T2 where user_id=100 and tag_id=4)
and tag_id=4;
EDIT: My question was not complete and had missing cases
here is an example (curtesy of #a_horse_with_no_name) http://sqlfiddle.com/#!12/67042/4
Thank you!
The outer join will already take care of what you want.
As t1 is the "left table" of the join, all rows from t1 will be returned. Columns from the "right table" (t2 in your example) will then have a null value. So you only need to convert that null to a 0:
select t1.tag_id, coalesce(t2.cnt, 0)
from T1 t1
left join T2 t2 on t1.tag_Id=t2.tag_id
and t1.place_id = 1;
SQLFiddle example: http://sqlfiddle.com/#!12/ed7bf/1
Unrelated but:
Using count as a column name is a really bad idea, because it will require you to always enclose the column name in double quotes: t2."count" because it is a reserved word. Plus it doesn't really document the purpose of the column. You should find a better name for that.
Let's say I have this table:
|Fld | Number|
1 5
2 2
And I want to make a select that retrieves as many Fld as the Number field has:
|Fld |
1
1
1
1
1
2
2
How can I achieve this? I was thinking about making a temporary table and instert data based on the Number, but I was wondering if this could be done with a single Select statement.
PS: I'm new to SQL
You can join with a numbers table:
SELECT Fld
FROM yourtable
JOIN Numbers
ON yourtable.Number <= Numbers.Number
A numbers table is just a table with a list of numbers:
Number
1
2
3
etc...
Not an great solution (since you still query your table twice, but maybe you can work from it)
SELECT t1.fld, t1.number
FROM table t1, (
SELECT ROWNUM number FROM dual
CONNECT BY LEVEL <= (SELECT MAX(number) FROM t1)) t2
WHERE t2.number<=t1.number
It generates maximum amount of rows needed and then filters it by each row.
I don't know if your RDBMS version supports it (although I rather suspect it does), but here is a recursive version:
WITH remaining (fld, times) as (SELECT fld, 1
FROM <table>
UNION ALL
SELECT a.fld, a.times + 1
FROM remaining as a
JOIN <table> as b
ON b.fld = a.fld
AND b.number > a.times)
SELECT fld
FROM remaining
ORDER BY fld
Given your source data table, it outputs this (count included for verification):
fld times
=============
1 1
1 2
1 3
1 4
1 5
2 1
2 2
I have result of two queries like:
Result of query 1
ID Value
1 4
2 0
3 6
4 9
Result of query 2
ID Value
1 6
2 4
3 0
4 1
I want to add values column "Value" and show final result:
Result of Both queries
ID Value
1 10
2 4
3 6
4 10
plz guide me...
select id, sum(value) as value
from (
select id, value from query1
uninon all
select id, value from query2
) x
group by id
Try using a JOIN:
SELECT
T1.ID,
T1.Value + T2.Value AS Value
FROM (...query1...) AS T1
JOIN (...query2...) AS T2
ON T1.Id = T2.Id
You may also need to consider what should happen if there is an Id present in one result but not in the other. The current query will omit it from the results. You may want to investigate OUTER JOIN as an alternative.
A not particularly nice but fairly easy to comprehend way would be:
SELECT ID,SUM(Value) FROM
(
(SELECT IDColumn AS ID,ValueColumn AS Value FROM TableA) t1
OUTER JOIN
(SELECT IDColumn AS ID,ValueColumn AS Value FROM TableB) t2
) a GROUP BY a.ID
It has the benefits of
a) I don't know your actual table structure so you should be able to work out how to get the two 'SELECT's working from your original queries
b) If ID doesn't appear in either table, that's fine