I have this table:
id value
AA000001 500
AA000002 1000
AA000003 1500
AA000004 2000
AA000005 2500
AA000006 3000
AA000007 3500
The type of id is a string and I use below sql statement to query my record:
SELECT sum(value), max(value), min(value) FROM my_table WHERE id BETWEEN 'AA000001' AND 'AA000007'
And it's works as expected. But I wonder if there are any exceptions in this query?
I'm using Oracle 10g Release 2 and 11g Release 2.
Thanks in advances.
I'm not exactly sure what you mean by "exceptions". Your query is:
SELECT sum(value), max(value), min(value)
FROM my_table
WHERE id BETWEEN 'AA000001' AND 'AA000007';
It will match anything between these values. In addition to what is in your table, it will match, say, 'AA000003ZYW243'. You are safe that all matches will start with 'AA00000'. The next character will be between '1' and '7', and then anything can follow that (unless that character is a '7').
Related
There is a database in place with hourly timeseries data, where every row in the DB represents one hour. Example:
TIMESERIES TABLE
id date_and_time entry_category
1 2017/01/20 12:00 type_1
2 2017/01/20 13:00 type_1
3 2017/01/20 12:00 type_2
4 2017/01/20 12:00 type_3
First I used the GROUP BY statement to find the latest date and time for each type of entry category:
SELECT MAX(date_and_time), entry_category
FROM timeseries_table
GROUP BY entry_category;
However now, I want to find which is the date and time which is the LEAST RECENT among the datetime's I obtained with the query listed above. I will need to use somehow SELECT MIN(date_and_time), but how do I let SQL know I want to treat the output of my previous query as a "new table" to apply a new SELECT query on? The output of my total query should be a single value—in case of the sample displayed above, date_and_time = 2017/01/20 12:00.
I've tried using aliases, but don't seem to be able to do the trick, they only rename existing columns or tables (or I'm misusing them..).There are many questions out there that try to list the MAX or MIN for a particular group (e.g. https://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/ or Select max value of each group) which is what I have already achieved, but I want to do work now on this list of obtained datetime's. My database structure is very simple, but I lack the knowledge to string these queries together.
Thanks, cheers!
You can use your first query as a sub-query, it is similar to what you are describing as using the first query's output as the input for the second query. Here you will get the one row out put of the min date as required.
SELECT MIN(date_and_time)
FROM (SELECT MAX(date_and_time) as date_and_time, entry_category
FROM timeseries_table
GROUP BY entry_category)a;
Is this what you want?
SELECT TOP 1 MAX(date_and_time), entry_category
FROM timeseries_table
GROUP BY entry_category
ORDER BY MAX(date_and_time) ASC;
This returns ties. If you do not want ties, then include an additional sort key:
SELECT TOP 1 MAX(date_and_time), entry_category
FROM timeseries_table
GROUP BY entry_category
ORDER BY MAX(date_and_time) ASC, entry_category;
I have table MYTABLE with columns mydate and quantity of VARCHAR2 type.
|mydate| |quantity|
10/15/2010 15
01/20/2010 20
05/16/2005 30
04/29/2005 50
03/30/2008 5
I want to get:
|year| |quantity|
2010 35
2005 80
2008 5
I try:
SELECT
to_char(mydate,'yyyy') YEAR,
SUM(to_number(quantity))
FROM MYTABLE
GROUP BY
to_char(mydate,'yyyy');
But I get an error
ORA-00979: not a GROUP BY expression
What did I do wrong?
You must put all columns of the SELECT in the GROUP BY or use functions on them which compress the results to a single value (like MIN, MAX or SUM).
A simple example to understand why this happens: Imagine you have a database like this:
FOO BAR
0 A
0 B
and you run SELECT * FROM table GROUP BY foo. This means the database must return a single row as result with the first column 0 to fulfill the GROUP BY but there are now two values of bar to chose from. Which result would you expect - A or B? Or should the database return more than one row, violating the contract of GROUP BY?
Try this
select extract(year from mydate),sum(to_number(quant)) from mytable
group by extract(year from mydate);
SQLFiddle Example
i have read tons of articles regarding last n records in Oracle SQL by using rownum functionality, but on my case it does not give me the correct rows.
I have 3 columns in my table: 1) message (varchar), mes_date (date) and mes_time (varchar2).
Inside lets say there is 3 records:
Hello world | 20-OCT-14 | 23:50
World Hello | 21-OCT-14 | 02:32
Hello Hello | 20-OCT-14 | 23:52
I want to get the last 2 records ordered by its date and time (first row the oldest, and second the newest date/time)
i am using this query:
SELECT *
FROM (SELECT message
FROM messages
ORDER
BY MES_DATE, MES_TIME DESC
)
WHERE ROWNUM <= 2 ORDER BY ROWNUM DESC;
Instead of getting row #3 as first and as second row #2 i get row #1 and then row #3
What should i do to get the older dates/times on top follow by the newest?
Maybe that helps:
SELECT *
FROM (SELECT message,
mes_date,
mes_time,
ROW_NUMBER() OVER (ORDER BY TO_DATE(TO_CHAR(mes_date, 'YYYY-MM-DD') || mes_time, 'YYYY-MM-DD HH24:MI') DESC) rank
FROM messages
)
WHERE rank <= 2
ORDER
BY rank
I am really sorry to disappoint - but in Oracle there's no such thing as "the last two records".
The table structure does not allocate data at the end, and does not keep a visible property of time (the only time being held is for the sole purpose of "flashback queries" - supplying results as of point in time, such as the time the query started...).
The last inserted record is not something you can query using the database.
What can you do? You can create a trigger that orders the inserted records using a sequence, and select based on it (so SELECT * from (SELECT * FROM table ORDER BY seq DESC) where rownum < 3) - that will assure order only if the sequence CACHE value is 1.
Notice that if the column that contains the message date does not have many events in a second, you can use that column, as the other solution suggested - e.g. if you have more than 2 events that arrive in a second, the query above will give you random two records, and not the actual last two.
AGAIN - Oracle will not be queryable for the last two rows inserted since its data structure do not managed orders of inserts, and the ordering you see when running "SELECT *" is independent of the actual inserts in some specific cases.
If you have any questions regarding any part of this answer - post it down here, and I'll focus on explaining it in more depth.
select * from table
minus
select * from table
where rownum<=(select count(*) from table)-n
I have this table:
ID Price Time
0 20,00 20/10/10
1 20,00 20/10/10
2 20,00 12/12/10
3 14,00 23/01/12
4 87,00 30/07/14
4 20,00 30/07/14
I use this syntax sql to get the list of all prices in a way that does not get repeated values:
SELECT * FROM myTable WHERE id in (select min(id) from %# group by Price)
This code return me the values (20,14,87,20)
But in this case I would implement another check, that will not only sort by price but also by date, example: That syntax is getting the list by price, if I find a way to check by date, the code will return me the values (20,20,14,87,20)
He repeats 20 two times but if we see in the table we have three numbers 20 (two with the date 20/10/10 and one with the date 12/12/10) and is exactly what I'm wanting to get!
Somebody could help me?
To group by multiple columns, just put a comma in between the list.
SELECT price FROM myTable group by price, time order by time
The group by looks at all distinct combinations of the listed columns values, and discards duplicates. You can also use aggregate functions like sum or max to pull in additional columns to the results.
The following should work as long as all you need is the price/time combination. If you need to include the ID, things get more complicated:
SELECT `Price` FROM items
GROUP BY `Price`, `Time`
ORDER BY `Time`;
Here's a fiddle with the result in action: http://sqlfiddle.com/#!2/40821/1
I am working on oracle10g. I was curious to know that is there any SQL function which may give results from the starting alphabet of a string.
For example, if I have road-1, road-A, road-89 and I want to know total number of such road sets without using the sql count() function.
For values that start with road:
SELECT YourColumn, COUNT(*) Total
FROM YourTable
WHERE YourColumn LIKE 'road%'
For values that contains road somewhere:
SELECT YourColumn, COUNT(*) Total
FROM YourTable
WHERE YourColumn LIKE '%road%'