I have a table with 3 columns VALUE1, step,date with values as given below....Now i want a view with a 4th column like below picture. for example, the maximum value of date for value1 '1' is 13.3.2014 and its corresponding step is C...So, the value of max(step-date) for '1' should be 'C' and so on. I want to do this without performing a join on the table itself. Hope am clear in my requirement. Thanks in advance.
You want to use analytical functions:
first_value(step) over (partition by value1 order by date_ desc)
first_value (step) tells Oracle that you want to get the first value of a list of steps. The elements and order of these is speciefied in the paranthesis after the over clause.
The "lists" are created with the partition by value1. Since there are two different value1's, two lists are created. The list belonging to value1 constists of the elements A, B and C, the list belonging to value2 of the elements A and B. These lists are ordered with the order by date_ desc clause.
Then, Oracle can "return" the first element of these lists.
See also this SQL fiddle
You want the last value based on date. You can do that with Oracle using an analytic function:
select Value1, step, date,
max(step) keep (dense_rank last order by date) over (partition by value1) as maxval
from table t;
The important part here is the keep part and the part after that. The keep (dense_rank last order by date) says to get the last value by date. The over (partition by value1) says to do that within groups where value1 has the same value.
Sigh, they beat me to the punch....
Here's my SQL Fiddle
Related
There is a table with the following column headers: indi_cod, ries_cod, date, time and level. Each ries_cod contains more than one indi_cod, and these indi_cod are random consecutive numbers.
Which SQL query would be appropriate to build if the aim is to find the smallest ID of each ries_cod, and at the same time bring its related information corresponding to date, time and level?
I tried the following query:
SELECT MIN (indi_cod) AS min_indi_cod
FROM my-project-01-354113.indi_cod.second_step
GROUP BY ries_cod
ORDER BY ries_cod
And, indeed, it presented me with the minimum value of indi_cod for each group of ries_cod, but I couldn't write the appropriate query to bring me the information from the date, time and level columns corresponding to each indi_cod.
I usually use some kind of ranking for this type of thing. you can use row_number, rank, or dense_rank depending on your rdbms. here is an example.
with t as(select a.*,
row_number() over (partition by ries_cod, order by indi_cod) as rn
from mytable)
select * from t where rn = 1
in addition if you are using oracle you can do this without two queries by using keep.
https://renenyffenegger.ch/notes/development/databases/SQL/select/group-by/keep-dense_rank/index
I think you just need to group by with the other columns
SELECT MIN (indi_cod), ries_cod, date, time, level AS min_indi_cod
FROM mytavke p
GROUP BY ries_cod, date, time, level
ORDER BY ries_cod
In BigQuery, I am trying to copy column values into other rows using a PARTITION BY statement anchored to a particular ID number.
Here is an example:
Right now, I am trying to use:
MIN(col_a) OVER (PARTITION BY CAST(id AS STRING), date ORDER BY date) AS col_b
It doesn't seem like the aggregate function is working properly. As in, the "col_b" still has null values when I try this method. Am I misunderstanding how aggregate functions work?
You can use this:
MIN(col_a) OVER (PARTITION BY id) AS col_b
If you have one value per id, this will return that value.
Note that converting id to a string is unnecessary. Also, you don't need a cumulative minimum, hence no ORDER BY.
Another option using coalesce
select *, coalesce(col_a, (select min(col_a) from my_table b where a.id=b.id)) col_b
from my_table a;
DEMO
This is a very simple question but I can't seem to find documentation on it. How one would query rows by index (ie select the 10th through 20th row in a table)?
I know there's a row_numbers function but it doesn't seem to do what I want.
Do not specify any partition so your row number will be an integer between 1 and your number of record.
SELECT row_num FROM (
SELECT row_number() over () as row_num
FROM your_table
)
WHERE row_num between 100000 and 100010
I seem to have found a roundabout and clunky way of doing this in Athena, so any better answers are welcome. This approach requires you have some numeric column in your table already, in this case named some_numeric_column:
SELECT some_numeric_column, row_num FROM (
SELECT some_numeric_column,
row_number() over (order by some_numeric_column) as row_num
FROM your_table
)
WHERE row_num between 100000 and 100010
To explain, you first select some numeric column in your data, then create a column (called row_num) of row numbers which is based on the order of your selected numeric column. Then you wrap that all in a select call because Athena doesn't support creating and then conditioning on the row_num column within a single call. If you don't wrap it in a second SELECT call Athena will spit out some errors about not finding a column named row_num.
I have a table as follows:
ParentActivityID | ActivityID | Timestamp
1 A1 T1
2 A2 T2
1 A1 T1
1 A1 T5
I want to select unique ParentActivityID's along with Timestamp. The time stamp can be the most recent one or the first one as is occurring in the table.
I tried to use DISTINCT but i came to realise that it dosen't work on individual columns. I am new to SQL. Any help in this regard will be highly appreciated.
DISTINCT is a shorthand that works for a single column. When you have multiple columns, use GROUP BY:
SELECT ParentActivityID, Timestamp
FROM MyTable
GROUP BY ParentActivityID, Timestamp
Actually i want only one one ParentActivityID. Your solution will give each pair of ParentActivityID and Timestamp. For e.g , if i have [1, T1], [2,T2], [1,T3], then i wanted the value as [1,T3] and [2,T2].
You need to decide what of the many timestamps to pick. If you want the earliest one, use MIN:
SELECT ParentActivityID, MIN(Timestamp)
FROM MyTable
GROUP BY ParentActivityID
Try this:
SELECT [ParentActivityId],
MIN([Timestamp]) AS [FirstTimestamp],
MAX([Timestamp]) AS [RecentTimestamp]
FROM [Table]
GROUP BY [ParentActivityId]
This will provide you the first timestamp and the most recent timestamp for each ParentActivityId that is present in your table. You can choose the ones you need as per your need.
"Group by" is what you need here. Just do "group by ParentActivityID" and tell that most recent timestamp along all rows with same ParentActivityID is needed for you:
SELECT ParentActivityID, MAX(Timestamp) FROM Table GROUP BY ParentActivityID
"Group by" operator is like taking rows from a table and putting them in a map with a key defined in group by clause (ParentActivityID in this example). You have to define how grouping by will handle rows with duplicate keys. For this you have various aggregate functions which you specify on columns you want to select but which are not part of the key (not listed in group by clause, think of them as a values in a map).
Some databases (like mysql) also allow you to select columns which are not part of the group by clause (not in a key) without applying aggregate function on them. In such case you will get some random value for this column (this is like blindly overwriting value in a map with new value every time). Still, SQL standard together with most databases out there will not allow you to do it. In such case you can use min(), max(), first() or last() aggregate function to work around it.
Use CTE for getting the latest row from your table based on parent id and you can choose the columns from the entire row of the output .
;With cte_parent
As
(SELECT ParentActivityId,ActivityId,TimeStamp
, ROW_NUMBER() OVER(PARTITION BY ParentActivityId ORDER BY TimeStamp desc) RNO
FROM YourTable )
SELECT *
FROM cte_parent
WHERE RNO =1
I've tried this query:
SELECT X,Y,Z,COUNT(*)
FROM TABLE1
GROUP BY X,Y,Z
and my result is:
but I need the following result:
This should do the trick:
SELECT X,Y,Z,ROW_NUMBER() OVER (PARTITION BY X,Y,Z ORDER BY X,Y,Z)
FROM TABLE1
The ROW_NUMBER() will tick up for every value in the group X,Y,Z, and reset at a next group. The ORDER BY clause is used to define in what order it should tick up, and can be changed to however you wish. This is one of the analytical functions Oracle provides, and can be very useful.