I have a table with this structure:
ID Version Content
-------------------------------------------------------
1 1 sometext
1 2 anothertext
1 3 someverydifferenttext
So all rows have the same ID but a different Version. I want to copy these rows (Insert Statement) and increase the Version-Column to the next free number.
Expected Result:
ID Version Content
-------------------------------------------------------
1 1 sometext
1 2 anothertext
1 3 someverydifferenttext
1 4 sometext
1 5 anothertext
1 6 someverydifferenttext
Is there way to do this in a single Select-Insert Statement?
I tried with...
Insert Into MyTable
SELECT ID
, MAX([Version])OVER(PARTITION BY ID ORDER BY [Version] DESC) + 1
,Content
FROM MyTable
But this does not work because MAX() would have to be evaluated again after each individual insert of a row. And the only option I currently see is a loop.
I use T-SQL.
Seems you could achieve this with ROW_NUMBER and a windowed MAX:
INSERT INTO dbo.YourTable
SELECT ID,
ROW_NUMBER() OVER (ORDER BY Version) + MAX(Version) OVER () AS Version,
Content
FROM dbo.YourTable WITH (UPDLOCK, HOLDLOCK);
db<>fiddle
Related
Okay, so this table will work as an example of what I am working with. This table consists of the name of someone and the order they are in compared to others:
NAME
ORDER
ZAC
1
JEFF
2
BART
3
KATE
4
My goal is to take the numbers in ORDER and reposition them randomly and update that into the table, keeping the NAME records in the same position that they were in originally.
Example of the desired result:
NAME
ORDER
ZAC
3
JEFF
1
BART
4
KATE
2
Using the table above, I have tried the following solutions:
#1
Update TEST_TABLE
Set ORDER = dbms_random.value(1,4);
This resulted in the random numbers between 1 and 4 inclusive, but the numbers could repeat, so ORDER could have the same number multiple times
Example of the attempted solution:
NAME
ORDER
ZAC
3
JEFF
1
BART
3
KATE
2
#2
Update TEST_TABLE
Set ORDER = (Select dbms_random.value(1,4) From dual);
This resulted in the same random number being copied into each ORDER record, so if the number came out at 3, then it would change them all to 3.
Example of the attempted solution:
NAME
ORDER
ZAC
3
JEFF
3
BART
3
KATE
3
This is my first time posting to StackOverflow, and I am relatively new to Oracle, so hopefully I proposed this question properly.
How about this?
Sample data:
SQL> select * from test order by rowid;
NAME C_ORDER
---- ----------
Zac 1
Jeff 2
Bart 3
Kate 4
Table is updated based on value acquired by the row_number analytic function which sorts data randomly; matches are found by the rowid value:
SQL> merge into test a
2 using (with counter (cnt) as
3 (select count(*) from test)
4 select t.rowid rid,
5 row_number() over(order by dbms_random.value(1, c.cnt)) rn
6 from counter c cross join test t
7 ) b
8 on (a.rowid = b.rid)
9 when matched then update set
10 a.c_order = b.rn;
4 rows merged.
Result:
SQL> select * from test order by rowid;
NAME C_ORDER
---- ----------
Zac 3
Jeff 4
Bart 1
Kate 2
SQL>
How about this?
MERGE INTO test d USING
(SELECT rownum AS new_order,
name
FROM (SELECT *
FROM test
ORDER BY dbms_random.value)) s
ON (d.name = s.name)
WHEN matched THEN
UPDATE
SET d.sort_order = s.new_order;
The new order is build by simply sorting the original data by random values and using rownum to number those random records from 1 to N.
I use NAME to match the records, but you should use the primary key or rowid as in Littlefoot answer.
Or at least an indexed column (for speed, when the table contains a lot of data), which uniquely identifies a row.
The simplest is to sort the data randomly and join on the "name" column:
merge into data dst
using (
select rownum as rn, name from (
select name from data order by dbms_random.value()
)
) src
on (src.name = dst.name)
when matched then
update set ord = src.rn
;
How to repeat rows based on column value in snowflake using sql.
I tried a few methods but not working such as dual and connect by.
I have two columns: Id and Quantity.
For each ID, there are different values of Quantity.
So if you have a count, you can use a generator:
with ten_rows as (
select row_number() over (order by null) as rn
from table(generator(ROWCOUNT=>10))
), data(id, count) as (
select * from values
(1,2),
(2,4)
)
SELECT
d.*
,r.rn
from data as d
join ten_rows as r
on d.count >= r.rn
order by 1,3;
ID
COUNT
RN
1
2
1
1
2
2
2
4
1
2
4
2
2
4
3
2
4
4
Ok let's start by generating some data. We will create 10 rows, with a QTY. The QTY will be randomly chosen as 1 or 2.
Next we want to duplicate the rows with a QTY of 2 and leave the QTY =1 as they are.
Obviously you can change all parameters above to suit your needs - this solution works super fast and in my opinion way better than table generation.
Simply stack SPLIT_TO_TABLE(), REPEAT() with a LATERAL() join and voila.
WITH TEN_ROWS AS (SELECT ROW_NUMBER()OVER(ORDER BY NULL)SOME_ID,UNIFORM(1,2,RANDOM())QTY FROM TABLE(GENERATOR(ROWCOUNT=>10)))
SELECT
TEN_ROWS.*
FROM
TEN_ROWS,LATERAL SPLIT_TO_TABLE(REPEAT('hire me $10/hour',QTY-1),'hire me $10/hour')ALTERNATIVE_APPROACH;
I'd like to update a certain column in a table based on the difference in a another column value between neighboring rows in PostgreSQL.
Here is a test setup:
CREATE TABLE test(
main INTEGER,
sub_id INTEGER,
value_t INTEGER);
INSERT INTO test (main, sub_id, value_t)
VALUES
(1,1,8),
(1,2,7),
(1,3,3),
(1,4,85),
(1,5,40),
(2,1,3),
(2,2,1),
(2,3,1),
(2,4,8),
(2,5,41);
My goal is to determine in each group main starting from sub_id 1 which value in diff exceeds a certain threshold (e.g. <10 or >-10) by checking in ascending order by sub_id. Until the threshold is reached I would like to flag every passed row AND the one row where the condition is FALSE by filling column newval with a value e.g. 1.
Should I use a loop or are there smarter solutions?
The task description in pseudocode:
FOR i in GROUP [PARTITION BY main ORDER BY sub_id]:
DO until diff > 10 OR diff <-10
SET newval = 1 AND LEAD(newval) = 1
Basic SELECT
As fast as possible:
SELECT *, bool_and(diff BETWEEN -10 AND 10) OVER (PARTITION BY main ORDER BY sub_id) AS flag
FROM (
SELECT *, value_t - lag(value_t, 1, value_t) OVER (PARTITION BY main ORDER BY sub_id) AS diff
FROM test
) sub;
Fine points
Your thought model evolves around the window function lead(). But its counterpart lag() is a bit more efficient for the purpose, since there is no off-by-one error when including the row before the big gap. Alternatively, use lead() with inverted sort order (ORDER BY sub_id DESC).
To avoid NULL for the first row in the partition, provide value_t as default as 3rd parameter, which makes the diff 0 instead of NULL. Both lead() and lag() have that capability.
diff BETWEEN -10 AND 10 is slightly faster than #diff < 11 (clearer and more flexible, too). (# being the "absolute value" operator, equivalent to the abs() function.)
bool_or() or bool_and() in the outer window function is probably cheapest to mark all rows up to the big gap.
Your UPDATE
Until the threshold is reached I would like to flag every passed row AND the one row where the condition is FALSE by filling column newval with a value e.g. 1.
Again, as fast as possible.
UPDATE test AS t
SET newval = 1
FROM (
SELECT main, sub_id
, bool_and(diff BETWEEN -10 AND 10) OVER (PARTITION BY main ORDER BY sub_id) AS flag
FROM (
SELECT main, sub_id
, value_t - lag(value_t, 1, value_t) OVER (PARTITION BY main ORDER BY sub_id) AS diff
FROM test
) sub
) u
WHERE (t.main, t.sub_id) = (u.main, u.sub_id)
AND u.flag;
Fine points
Computing all values in a single query is typically substantially faster than a correlated subquery.
The added WHERE condition AND u.flag makes sure we only update rows that actually need an update.
If some of the rows may already have the right value in newval, add another clause to avoid those empty updates, too: AND t.newval IS DISTINCT FROM 1
See:
How do I (or can I) SELECT DISTINCT on multiple columns?
SET newval = 1 assigns a constant (even though we could use the actually calculated value in this case), that's a bit cheaper.
db<>fiddle here
Your question was hard to comprehend, the "value_t" column was irrelevant to the question, and you forgot to define the "diff" column in your SQL.
Anyhow, here's your solution:
WITH data AS (
SELECT main, sub_id, value_t
, abs(value_t
- lead(value_t) OVER (PARTITION BY main ORDER BY sub_id)) > 10 is_evil
FROM test
)
SELECT main, sub_id, value_t
, CASE max(is_evil::int)
OVER (PARTITION BY main ORDER BY sub_id
ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING)
WHEN 1 THEN NULL ELSE 1 END newval
FROM data;
I'm using a CTE to prepare the data (computing whether a row is "evil"), and then the "max" window function is used to check if there were any "evil" rows before the current one, per partition.
EXISTS on an aggregating subquery:
UPDATE test u
SET value_t = NULL
WHERE EXISTS (
SELECT * FROM (
SELECT main,sub_id
, value_t , ABS(value_t - lag(value_t)
OVER (PARTITION BY main ORDER BY sub_id) ) AS absdiff
FROM test
) x
WHERE x.main = u.main
AND x.sub_id <= u.sub_id
AND x.absdiff >= 10
)
;
SELECT * FROM test
ORDER BY main, sub_id;
Result:
UPDATE 3
main | sub_id | value_t
------+--------+---------
1 | 1 | 8
1 | 2 | 7
1 | 3 | 3
1 | 4 |
1 | 5 |
2 | 1 | 3
2 | 2 | 1
2 | 3 | 1
2 | 4 | 8
2 | 5 |
(10 rows)
I am using oracle 12c database and I have a table with the following structure:
Id NUMBER
SeqNo NUMBER
Val NUMBER
Valid VARCHAR2
A composite primary key is created with the field Id and SeqNo.
I would like to fetch the data with Valid = 'Y' and apply ketset pagination with a page size of 3. Assume I have the following data:
Id SeqNo Val Valid
1 1 10 Y
1 2 20 N
1 3 30 Y
1 4 40 Y
1 5 50 Y
2 1 100 Y
2 2 200 Y
Expected result:
----------------------------
Page 1
----------------------------
Id SeqNo Val Valid
1 1 10 Y
1 3 30 Y
1 4 40 Y
----------------------------
Page 2
----------------------------
Id SeqNo Val Valid
1 5 50 Y
2 1 100 Y
2 2 200 Y
Offset pagination can be done like this:
SELECT * FROM table ORDER BY Id, SeqNo OFFSET 3 ROWS FETCH NEXT 3 ROWS ONLY;
However, in the actual db it has more than 5 millions of records and using OFFSET is going to slow down the query a lot. Therefore, I am looking for a ketset pagination approach (skip records using some unique fields instead of OFFSET)
Since a composite primary key is used, I need to offset the page with information from more than 1 field.
This is a sample SQL that should work in PostgreSQL (fetch 2nd page):
SELECT * FROM table WHERE (Id, SeqNo) > (1, 4) AND Valid = 'Y' ORDER BY Id, SeqNo LIMIT 3;
How do I achieve the same in oracle?
Use row_number() analytic function with ceil arithmetic fuction. Arithmetic functions don't have a negative impact on performance, and row_number() over (order by ...) expression automatically orders the data without considering the insertion order, and without adding an extra order by clause for the main query. So, consider :
select Id,SeqNo,
ceil(row_number() over (order by Id,SeqNo)/3) as page
from tab
where Valid = 'Y';
P.S. It also works for Oracle 11g, while OFFSET 3 ROWS FETCH NEXT 3 ROWS ONLY works only for Oracle 12c.
Demo
You can use order by and then fetch rows using fetch and offset like following:
Select ID, SEQ, VAL, VALID FROM TABLE
WHERE VALID = 'Y'
ORDER BY ID, SEQ
--FETCH FIRST 3 ROWS ONLY -- first page
--OFFSET 3 ROWS FETCH NEXT 3 ROWS ONLY -- second pages
--OFFSET 6 ROWS FETCH NEXT 3 ROWS ONLY -- third page
--Update--
You can use row_number analytical function as following.
Select id, seqNo, Val, valid from
(Select t.*,
Row_number(order by id, seq) as rn from table t
Where valid = 'Y')
Where ceil(rn/3) = 2 -- for page no. 2
Cheers!!
I am pretty new to SQL and I thought I was comfortable using it after a while but it still is tough. I am trying to increment ids. I know I could use auto-increment but in this case there are id has relationship with several categories so it has to start with different numbers so I can't do it.
The table looks something like this:
id category
----------------
1000 1
1000 1
...
2000 2
2000 2
...
And I want to make it:
id category
------------------
1000 1
1001 1
1002 1
...
2000 2
2001 2
...
I tried:
UPDATE T1
SET id = CASE
WHEN EXISTS (SELECT id FROM STYLE WHERE T1.id = id)
THEN (SELECT MAX(CAST(id AS INT)) + 1
FROM STYLE
WHERE category = T1.category)
END
FROM STYLE T1
WHERE idStyle = idStyle
But it just added 1 to all rows. How could I go 1 by 1 so it could actually get the incremented max id? Thank you.
In the absense of real sample data, this is a pseudo-sql, however, something like...
UPDATE YT
----SELECT NULL as Ihave no context of other fields in your table
SET id = id + ROW_NUMBER() OVER (PARTITION BY category ORDER BY (SELECT NULL)) - 1
FROM YourTable YT;
You can use row_number() function instead :
select *,
concat(cid, row_number() over (partition by id order by category)-1) as NewId
from style s;