I have a column like this:
ID
--------
1
2
3
4
5
7
10
and I want to get the following resultset:
ID
--------
1-5
7
10
Is there a way to achieve this with (Oracle) SQL only?
Yes:
select (case when min(id) < max(id)
then cast(min(id) as varchar2(255)) || '-' || cast(max(id) as varchar2(255))
else cast(min(id) as varchar2(255))
end)
from (select id, id - rownum as grp
from t
order by id
) t
group by grp
order by min(id);
Here is a SQL Fiddle demonstrating it.
The idea behind the query is that subtracting rownum from a sequence of numbers results in a constant. You can use the constant for grouping.
self joins are necessary... I think this will work
Select a.id, b.id
From table a -- to get beginning of each range
Join table b -- to get end of each range
On b.id >= a.Id -- guarantees that b is after a
And Not exists (Select * From table m -- this guarantees all values between
where id Between a.id+1 and b.id
And Not exists(Select * From table
Where id = m.id-1))
And Not exists (Select * From table -- this guarantees that table a is start
Where id = a.id -1)
And Not exists (Select * From table -- this guarantees that table b is end
Where id = b.id + 1)
Related
I am trying to write a query to delete duplicate records based on a ID and a value. There are multiple rows with the same ID. Condition to get the result are (and the queries I have written as per my understanding),
Look for maximum value available for the ID column in Value column (SELECT * FROM TABLE WHERE VALUE IN (SELECT MAX(VALUE) FROM TABLE GROUP BY ID)
Example:
Table data:
ID - Value
a - 1
a - 2
a - 3
b - 2
c - 3
Output:
ID - Value
a - 3
b - 2
c - 3
Ignore the results from point 1 in the table (SELECT * FROM TABLE WHERE NOT EXISTS ((SELECT * FROM TABLE WHERE VALUE IN (SELECT MAX(VALUE) FROM TABLE GROUP BY ID))
Edit: I wrote a query that finally outputs the required result for point 2
SELECT t1.* FROM TABLE t1
LEFT JOIN
(
SELECT 1 AS aux, * FROM (SELECT * FROM TABLE
WHERE VALUE IN
(SELECT MAX(VALUE) FROM TABLE group by ID))
) t2
ON
t2.ID= t1.ID
and
t2.VALUE= t1.VALUE
WHERE t2.aux IS NULL
Example:
Table data:
ID - Value
a - 1
a - 2
a - 3
b - 2
c - 3
Output:
ID - Value
a - 1
a - 2
Use the query of point 2 to delete rows from table (DELETE FROM TABLE WHERE (ID,VALUE) IN (SELECT * FROM TABLE WHERE NOT EXISTS ((SELECT * FROM TABLE WHERE VALUE IN (SELECT MAX(VALUE) FROM TABLE GROUP BY ID)))
Example:
Table data:
ID - Value
a - 1
a - 2
a - 3
b - 2
c - 3
Table data:
ID - Value
a - 3
b - 2
c - 3
Point 2 does not work, it is giving no results. When the checked the total row of output of the query from point 2 and total row of the table, there is a difference.
Since point 2 does not work, point 3 fails as well. What am I doing wrong?
After our discussion, I understand that you aimed to select many rows of data which respects the filter id and max(value). Therefore, I can suggest you the following script:
SELECT
DISTINCT a.*
FROM
`test-proj-261014.sample.id_value` a
RIGHT JOIN (
SELECT
id,
MAX(value) AS max_val
FROM
`test-proj-261014.sample.id_value`
GROUP BY
id
ORDER BY
id) b
ON
a.id = b.id
AND a.value = b.max_val
WHERE
a.value IS NOT NULL
ORDER BY
id;
Not that I use SELECT DISTINCT, which will not select duplicated data. In addition, due to the possibility of the existence of null values, I added the consition***WHERE a.value IS NOT NULL***, which will not select the rows that do not respect the condition.
The above query should solve the problem, however if you find any discrepancy with the expected amount of rows, I encourage you explore your data set and detect the reason why there are extra or less rows. You can use different types of joins to do so, one example would be the following query:
SELECT
a.*
FROM
`test-proj-261014.sample.id_value` a
LEFT JOIN (
SELECT
id,
MAX(value) AS max_val
FROM
`test-proj-261014.sample.id_value`
GROUP BY
id
ORDER BY
id) b
ON
a.id = b.id
AND a.value = b.max_val
WHERE
b.max_val IS NULL
ORDER BY
id;
This query retrieves all the values which are not present in the final output generated by the first query. This would help you understand better the data you are dealing with.
I hope it helps.
I'm currently having trouble writing the business logic to get rows from a table with id's and a flag which I have appended to it.
For example,
id: id seq num: flag: Date:
A 1 N ..
A 2 N ..
A 3 N
A 4 Y
B 1 N
B 2 Y
B 3 N
C 1 N
C 2 N
The end result I'm trying to achieve is that:
For each unique ID I just want to retrieve one row with the condition for that row being that
If the flag was a "Y" then return that row.
Else return the last "N" row.
Another thing to note is that the 'Y' flag is not always necessarily the last
I've been trying to get a case condition using a partition like
OVER (PARTITION BY A."ID" ORDER BY A."Seq num") but so far no luck.
-- EDIT:
From the table, the sample result would be:
id: id seq num: flag: date:
A 4 Y ..
B 2 Y ..
C 2 N ..
Using a window clause is the right idea. You should partition the results by the ID (as you've done), and order them so the Y flag rows come first, then all the N flag rows in descending date order, and pick the first for each id:
SELECT id, id_seq_num, flag, date
FROM (SELECT id, id_seq_num, flag, date,
ROW_NUMBER() OVER (PARTITION BY id
ORDER BY CASE flag WHEN 'Y' THEN 0
ELSE 1
END ASC,
date ASC) AS rk
FROM mytable) t
WHERE rk = 1
My approach is to take a UNION of two queries. The first query simply selects all Yes records, assuming that Yes only appears once per ID group. The second query targets only those ID having no Yes anywhere. For those records, we use the row number to select the most recent No record.
WITH cte1 AS (
SELECT id
FROM yourTable
GROUP BY id
HAVING SUM(CASE WHEN flag = 'Y' THEN 1 ELSE 0 END) = 0
),
cte2 AS (
SELECT *,
ROW_NUMBER() OVER (PARTITION BY t1.id ORDER BY t1."id seq" DESC) rn
FROM yourTable t1
INNER JOIN cte1 t2
ON t1.id = t2.id
)
SELECT *
FROM yourTable
WHERE flag = 'Y'
UNION ALL
SELECT *
FROM cte2 t2
WHERE t2.rn = 1
Here's one way (with quite generic SQL):
select t1.*
from Table1 as t1
where t1.id_seq_num = COALESCE(
(select max(id_seq_num) from Table1 as T2 where t1.id = t2.id and t2.flag = 'Y') ,
(select max(id_seq_num) from Table1 as T3 where t1.id = t3.id and t3.flag = 'N') )
Available in a fiddle here: http://sqlfiddle.com/#!9/5f7f9/6
SELECT DISTINCT id, flag
FROM yourTable
I have a table that looks like this:
ID Type Value
A Z01 10
A Z09 20
B Z01 30
C Z01 40
D Z09 50
E Z10 60
For each ID I would like to retrieve a value. Ideally the value should come from the row with type Z01. However, if Z01 is not available I'll pick Z09 instead. If nothing is available I would like to select nothing.
The result would look like this:
Id Type Value
A Z01 10
B Z01 30
C Z01 40
D Z09 50
How can I accomplish this with T-SQL?
This should give you what you want:
select *
from table t
where 1 = case
when t.type = 'Z01'
then 1
when t.type = 'Z09'
and not exists (select 1 from table where id = t.id and type = 'Z01')
then 1
else 0
end
An alternative, with using a more common approach is (re-writing the CASE expression):
select *
from table
where type = 'Z01'
OR (type = 'Z09' and not exists (select 1 from table where id = t.id and type = 'Z01'))
An obvious sargable approach (which will make your query use the appropriate index on your table, if it exists) would be:
select *
from table
where type = `Z01`
union all
select *
from table
where type = `Z09`
and not exists (select 1 from table where id = t.id and type = 'Z01')
And when I'm saying index I'm talking about a non-clustered index on the type column.
You can use query like this
;WITH cte
AS (SELECT
*, ROW_NUMBER() OVER (PARTITION BY id ORDER BY type) AS rn
FROM yourtable
WHERE type IN ('Z01', 'Z09'))
SELECT
id, type, value
FROM cte
WHERE rn = 1
I would use window functions:
select t.*
from (select t.*,
row_number() over (partition by id
order by (case when type = 'Z01' then 1
when type = 'Z09' then 2
end)
) as seqnum
from t
) t
where seqnum = 1;
I don't fully understand teh statement "if nothing is available, then choose nothing". If, by this, you mean you want 'Z01', 'Z09' or nothing at all, then just do:
select t.*
from (select t.*,
row_number() over (partition by id order by type) as seqnum
from t
where type in ('Z01', 'Z09')
) t
where seqnum = 1;
The where clause does the filtering, and you can just order by the type alphabetically.
Something like this:
select distinct
base.Id,
Coalesce(z01.Type, any.Type) Type,
Coalesce(z01.Value, any.Value)
from (select distinct id from [table]) base
left outer join [table] z01
on z01.id = base.id
and z01.Type = 'Z01'
left outer join [table] any
on any.id = base.id
and any.type != 'Z01'
Start with a WHERE clause. Select only entries with Z01 and Z09. Then use ROW_NUMBER to rank your rows and keep the best.
select id, type, value
from
(
select
id, type, value,
row_number()
over (partition by id order by case when type = 'Z01' then 1 else 2 end) as rn
from mytable
where type in ('Z01','Z09')
) ranked
where rn = 1;
Then try this
Select distinct a.id,
coalesce(t1.type, t9.type) type,
case when t1.type is not null
then t1.value else t9.value end value
From table a
left join table t1
on t1.id = a.id
and t1.type = 'Z01'
left join table t9
on t9.id = a.id
and t9.type = 'Z09'
Where a.type in ('Z01', 'Z09') -- < -- this last to eliminate row E
I have two columns for example. A is a Varchar2 and B is a date column.
Data sample:
A B
---------- -----------
10/27/15
10/28/15 Y
How do I write a sql which will check max(A) record if B is NULL, and if it is then only select it. So in this scenario no rows should return.
I hope that made sense.
Here is one method:
select s.*
from (select s.*
from (select s.*
from sample s
order by a desc
) s
where rownum = 1
) s
where s.B is null;
This is slightly simpler in Oracle 12+:
select s.*
from (select s.*
from sample s
order by a desc
fetch first 1 row only
) s
where s.B is null;
An alternative uses conditional aggregation:
select max(a)
from sample
having max(a) = max(case when b is null then a end);
I require to select a row if there is only one row exists, if there are more rows, it should select 0 rows.
If you're using PL/SQL, then selecting the column using select-into will throw a too_many_rows exception if there's more than one row returned:
declare
var table.column%type;
begin
select column
into var
from table
where ...;
end;
If you want to do this just using SQL, then you can do something like:
select *
from
(select s.*, count(*) over () c
from
(select *
from table
where ...
and rownum <= 2
) s
)
where c = 1
UPDATE
As DazzaL says in the comments, the reason for the rownum <= 2 restriction is to short-circuit the query if there's more than 2 rows in the result set. This can give significant performance benefits if the dataset is large.
I came up with this, just for the heck of it, using a CTE
With counter as
( select count(any_field) as cnt from your_query
)
SELECT
your_query
WHERE exists (SELECT cnt from Counter WHERE cnt=1)
1 row when there's 1 record - http://sqlfiddle.com/#!4/84c7b/2
0 rows when more than 1 rec - http://sqlfiddle.com/#!4/95c4a/1
EDIT
or if you want to avoid repeating the whole query... an example :
(using the schema from sqlfiddle http://sqlfiddle.com/#!4/6a2d8/117 )
With results as
( select * from montly_sales_totals
),
counter as
( SELECT count(name) as cnt FROM results
)
SELECT *
FROM results
WHERE exists (SELECT cnt from Counter WHERE cnt=5)
SELECT fld1, fld2
FROM (SELECT COUNT(*) over() cnt ,fld1, fld2 FROM tbl WHERE fld1 = 'key')
WHERE cnt = 1
I require to select a row if there is only one row exists, if there
are more rows, it should select 0 rows.
I assume the table contains only the row(s) you are interested to see (or not to see), in that case I would write something like
select *
from table1
where 1 = (select count(1)
from table1
)
In case you want to see only one row from a subset of results from your table, I would go for something like:
with t as ( select *
from table1
where [put here your condition]
)
select *
from t
where 1 = (select count(1)
from t
)
Try this:
SELECT f1,f2
FROM Table
WHERE (f1 = #f1) AND (f2=#f2) AND (f3=#f3)
GROUP BY f1,f2
HAVING (COUNT(*) = 1)
DECLARE COL_COUNT NUMBER;
BEGIN
COL_COUNT: = 0 ;
SELECT COUNT (1) INTO COL_COUNT FROM USER_TAB_COLUMNS WHERE TABLE_NAME = '(ur table name)';
IF COL_COUNT = 0 THEN
EXECUTE IMMEDIATE ('select * from dual') ;
END IF;
END;
Try this:
SELECT col1, col2 FROM
(SELECT count(id) as 'cnt', col1, col2 FROM table_name WHERE col1='value')
WHERE cnt=1;