I have a Postgres 9.0 query returning results in a way similar to this:
item;qty
AAAA;2
EEEE;3
What I would like is to transform that into:
AAAA
AAAA
EEEE
EEEE
EEEE
Is there any way I can do that on simple, i.e., without stored procedures, functions, etc?
There's a function 'generate_series' which can be used to generate a table of values. These can be used to repeat a column via joining:
select item
from data,generate_series(0,1000)
where generate_series<qty order by item;
Consider the following demo:
CREATE TEMP TABLE x(item text, qty int);
INSERT INTO x VALUES
('AAAA',2)
,('EEEE',3)
,('IIII',4);
SELECT regexp_split_to_table(rtrim(repeat(item||'~#~',qty),'~#~'),'~#~') AS item
FROM x;
Produces exactly the requested result.
In my tests it performs faster by an order of magnitude than the solution with generate_series().
Additional bonus: works with any number of qty.
Weakness: you need a delimiter-string not contained in any item.
SELECT
myTable.item
FROM
myTable
INNER JOIN
(SELECT 1 AS counter UNION ALL SELECT 2 UNION ALL SELECT 3) AS multiplier
ON multiplier.counter <= myTable.qty
Increase the number of UNIONS based on your Maximum value in qty
But I'd also follow #djacobson's advice : explain why you want to do this, as the may be a completely different approach altogether. Doing this feels, ummm, odd...
Related
I'm just getting started with sql and have the objective to transform this:
select X.persnr
from Pruefung X
where X.persnr in (
select Y.persnr
from pruefung Y
where X.matrikelnr <> Y.matrikelnr)
output:
into the same output but using a form of join. I tried it the way below but I can't seem to get "rid" of the cartesian product as far as i can see. Or maybe i misunderstood the above statement what it should actually do. For me the above says "for each unique matrikelnr display all corresponding persnr".
select X.persnr
from Pruefung X
join pruefung y on x.persnr=y.persnr
where x.matrikelnr<>y.matrikelnr
output: A long list (I don't want to fill the entire question with it) - i am guessing the cartesian product from the join
This is the relation I am using.
Edit: Distinct (unless i am using it in the wrong place) won't work because then persnr is only displayed once, thats not the objective though.
Your initial query actually does:
select persnr from Pruefung if the same persnr exists for a a diferent matrikelnr.
"for each unique matrikelnr display all corresponding persnr"
This is achieved using aggregation:
Depending on the DBMS you are using you could use something like (SQL Server uses STRING_AGG, but MySQL uses GROUP_CONCAT)
SELECT matrikelnr,STRING_AGG(matrikelnr,',')
GROUP BY matrikelnr
You cannot easily achieve what you got from a correlated query (your first attempt) by using a join.
Edit:
A join does not result in a "Cartesian product" expect from when there is no join condition (CROSS JOIN).
A join matches two sets based on a join condition. The reason why you get more entries is that the join looks at the join key (PERSNR) and does its matching.
For example for 101 you have 3 entries. That means you will get 3x3 reults.
You then filter out the results for the cases where X.matrikelnr <> Y.matrikelnr If we assume matrikelnr is unique that would mean the row matched with itself. so you will lose 3 results ending up with 3x3 - 3 = 6.
If you want to achieve something in SQL you must first define what you are expecting to use and then use the appropiate tools (in this case correlated queries not joins)
You can write your 1st query with EXISTS instead of IN like:
select X.persnr
from Pruefung X
where exists (
select 1
from pruefung Y
where X.persnr = Y.persnr and X.matrikelnr <> Y.matrikelnr
)
This way it's obvious that this query means:
return all the persnrs of the table for which there exists another
row with the same persnr but different matrikelnr
For your sample data the result is all the persnrs of the table.
Your 2nd query though, does something different.
It links every row of the table with all the rows of the same table with the same persnr but different matrikelnr.
So for every row of the table you will get as many as rows as there are for the same persnrs but different matrikelnrs.
For example for the 1st row with persnr = 101 and matrikelnr = 8532478 you will get 2 rows because there are 2 rows in the table with persnr = 101 and matrikelnr <> 8532478.
You are right. It's the cartesian product's fault. Suppose you have persnr 1,1,1,2,2,2 in the first table and persnr 1,1,1,2,2 in the second. How many lines are you expecting to be returned?
In pdeuso-code it would go like this
Select
...
WHERE persnr in (second table)
-- 6 lines
Select persnr
FROM ...
JOIN ... ON a.persnr = b.persnr
-- 3X3 + 3X2 = 15 lines.
SELECT DISTINCT persnr
FROM ...
JOIN ... ON a.persnr = b.persnr
-- 2 lines (1 and 2)
Take your pick
I would love some help with the best way to capture some column data and rotate it so I can store the column name and numeric value in a temp table.
The results are a single row showing a value for the columns listed here:
AccountingCode ActiveCostAllocationCode1Segment1 ActiveCostAllocationCode1Segment1Description
-------------- --------------------------------- --------------------------------------------
0 71 264
I would like to take the above query and rotate the output to look more vertical.
ColName Value
--------------------------------------------- ---------
AccountingCode 0
ActiveCostAllocationCode1Segment1 71
ActiveCostAllocationCode1Segment1Description 264
I was trying to use PIVOT / UNPIVOT but could not figure how to make it work for this case.
Any ideas?
If you are working with SQL Sever then you can use APPLY :
SELECT tt.ColName, tt.val
FROM table t CROSS APPLY
( VALUES ('AccountingCode', AccountingCode),
('ActiveCostAllocationCode1Segment1', ActiveCostAllocationCode1Segment1),
('ActiveCostAllocationCode1Segment1Description', ActiveCostAllocationCode1Segment1Description)
) tt(ColName, Val);
In standard you can use UNION ALL to UNPIVOT the data.
The generic way in SQL is UNION ALL:
select 'AccountingCode', AccountingCode from t
union all
select 'ActiveCostAllocationCode1Segment1', ActiveCostAllocationCode1Segment1 from t
union all
select 'ActiveCostAllocationCode1Segment1Description', ActiveCostAllocationCode1Segment1Description
This assumes that the types of the columns are compatible (they all look like integers, so that is probably okay).
The better method is to use a lateral join (or apply in some databases), if your database supports it.
I've been looking at this this for the last hour and just can't seem to find a way to do it, I'm sure its pretty simple but my google and reading skills have failed me.
All I need to do is to find ascending and descending numerical patterns in a field.
Like in this pseudo-SQL Code:
select * where col = '123456' or '23456' or '7654' or '987654321'
Most of the pattern methods using LIKE seem to be around placement of characters/numbers rather than the specific ordering,
I've started trying to create a query than takes the first character and compares it to the next one but this seems really ineffective and inefficient as it would need to take each field in the column run the query and return it if it matches.
I've managed to find a way to get it if its a repeated character but not if its an increase or decrease.
Any help would be greatly appreciated.
You can put regular expression inside your LIKE quotes.
Ascending:
^(?=\d{4,10}$)1?2?3?4?5?6?7?8?9?0?$
Descending:
^(?=\d{4,10}$)9?8?7?6?5?4?3?2?1?0?$
d{4,10} here is possible value length, between 4 and 10 symbols.
Won't be fast, most likely.
You can check how it works on http://rubular.com/.
Edit: Sorry, I forgot to mention you will have to do a MS SQL Server CLR integration first. By default, MSSQL Server does not fully support RegEx.
This article describes how to create and use extensions for the LIKE (Transact-SQL) clause that supports Regular Expressions.
http://www.codeproject.com/Articles/42764/Regular-Expressions-in-MS-SQL-Server
Another option could be something like this:
Declare #Table table (col int)
Insert into #Table values
(4141243),(4290577),(98765432),(78635389),(4141243),(22222),(4290046),(55555555),(4141243),(6789),(77777),(45678),(4294461),(55555),(4141243),(5555)
Declare #Num table (Num int);Insert Into #Num values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)
Select Distinct A.*
From #Table A
Join (
Select Patt=replicate(Num,3) from #Num
Union All
Select Patt=right('000'+cast((Num*100+Num*10+Num)+12 as varchar(5)),3) from #Num where Num<8
Union All
Select Patt=reverse(right('000'+cast((Num*100+Num*10+Num)+12 as varchar(5)),3)) from #Num where Num<8
) B on CharIndex(Patt,cast(col as varchar(25)))>0
Returns
Col
5555
6789
22222
45678
55555
77777
55555555
98765432
**
Think RUMMY 500. A groups or runs of 3. For example 123 or 321 or
333 would be a hit.
**
I have a table which contains geometry lines (ways).There are lines that have a unique geometry (not repeating) and lines which have the same geometry (2,3,4 and more). I want to list only unique ones. If there are, for example, 2 lines with the same geometry I want to drop them. I tried DISTINCT but it also shows the first result from duplicated lines. I only want to see the unique ones.
I tried window function but I get similar result (I get a counter on first line from the duplicating ones). Sorry for a newbie question but I'm learning :) Thanks!
Example:
way|
1 |
1 |
2 |
3 |
3 |
4 |
Result should be:
way|
2 |
4 |
That actually worked. Thanks a lot. I also have other tags in this table for every way (name, ref and few other tags) When I add them to the query I loose the segregation.
select count(way), way, name
from planet_osm_line
group by way, name
having count(way) = 1;
Without "name" in the query I get all unique values listed but I want to keep "name" for every line. With this example I stilll get all the lines in the table listed.
To expound on #Nithila answer:
select count(way), way
from your_table
group by way
having count(way) = 1;
You first calculate the rows you want, and then search for the rest of the fields. So the aggregation doesnt cause you problems.
WITH singleRow as (
select count(way), way
from planet_osm_line
group by way
having count(way) = 1
)
SELECT P.*
FROM planet_osm_line P
JOIN singleRow S
ON P.way = S.way
you can group by way and while taking the data out check the count=1.It will give non duplicating data.
#voyteck
As I understood your question you need to get only non duplicating records of way column and for each row you need to show the name is it
If so, you have to put all the column in select statement, but no need to group by all the columns.
select count(way), way, name
from planet_osm_line
group by way
having count(way) = 1;
Hi I know how to use the group by clause for sql. I am not sure how to explain this so Ill draw some charts. Here is my original data:
Name Location
----------------------
user1 1
user1 9
user1 3
user2 1
user2 10
user3 97
Here is the output I need
Name Location
----------------------
user1 1
9
3
user2 1
10
user3 97
Is this even possible?
The normal method for this is to handle it in the presentation layer, not the database layer.
Reasons:
The Name field is a property of that data row
If you leave the Name out, how do you know what Location goes with which name?
You are implicitly relying on the order of the data, which in SQL is a very bad practice (since there is no inherent ordering to the returned data)
Any solution will need to involve a cursor or a loop, which is not what SQL is optimized for - it likes working in SETS not on individual rows
Hope this helps
SELECT A.FINAL_NAME, A.LOCATION
FROM (SELECT DISTINCT DECODE((LAG(YT.NAME, 1) OVER(ORDER BY YT.NAME)),
YT.NAME,
NULL,
YT.NAME) AS FINAL_NAME,
YT.NAME,
YT.LOCATION
FROM YOUR_TABLE_7 YT) A
As Jirka correctly pointed out, I was using the Outer select, distinct and raw Name unnecessarily. My mistake was that as I used DISTINCT , I got the resulted sorted like
1 1
2 user2 1
3 user3 97
4 user1 1
5 3
6 9
7 10
I wanted to avoid output like this.
Hence I added the raw id and outer select
However , removing the DISTINCT solves the problem.
Hence only this much is enough
SELECT DECODE((LAG(YT.NAME, 1) OVER(ORDER BY YT.NAME)),
YT.NAME,
NULL,
YT.NAME) AS FINAL_NAME,
YT.LOCATION
FROM SO_BUFFER_TABLE_7 YT
Thanks Jirka
If you're using straight SQL*Plus to make your report (don't laugh, you can do some pretty cool stuff with it), you can do this with the BREAK command:
SQL> break on name
SQL> WITH q AS (
SELECT 'user1' NAME, 1 LOCATION FROM dual
UNION ALL
SELECT 'user1', 9 FROM dual
UNION ALL
SELECT 'user1', 3 FROM dual
UNION ALL
SELECT 'user2', 1 FROM dual
UNION ALL
SELECT 'user2', 10 FROM dual
UNION ALL
SELECT 'user3', 97 FROM dual
)
SELECT NAME,LOCATION
FROM q
ORDER BY name;
NAME LOCATION
----- ----------
user1 1
9
3
user2 1
10
user3 97
6 rows selected.
SQL>
I cannot but agree with the other commenters that this kind of problem does not look like it should ever be solved using SQL, but let us face it anyway.
SELECT
CASE main.name WHERE preceding_id IS NULL THEN main.name ELSE null END,
main.location
FROM mytable main LEFT JOIN mytable preceding
ON main.name = preceding.name AND MIN(preceding.id) < main.id
GROUP BY main.id, main.name, main.location, preceding.name
ORDER BY main.id
The GROUP BY clause is not responsible for the grouping job, at least not directly. In the first approximation, an outer join to the same table (LEFT JOIN below) can be used to determine on which row a particular value occurs for the first time. This is what we are after. This assumes that there are some unique id values that make it possible to arbitrarily order all the records. (The ORDER BY clause does NOT do this; it orders the output, not the input of the whole computation, but it is still necessary to make sure that the output is presented correctly, because the remaining SQL does not imply any particular order of processing.)
As you can see, there is still a GROUP BY clause in the SQL, but with a perhaps unexpected purpose. Its job is to "undo" a side effect of the LEFT JOIN, which is duplication of all main records that have many "preceding" ( = successfully joined) records.
This is quite normal with GROUP BY. The typical effect of a GROUP BY clause is a reduction of the number of records; and impossibility to query or test columns NOT listed in the GROUP BY clause, except through aggregate functions like COUNT, MIN, MAX, or SUM. This is because these columns really represent "groups of values" due to the GROUP BY, not just specific values.
If you are using SQL*Plus, use the BREAK function. In this case, break on NAME.
If you are using another reporting tool, you may be able to compare the "name" field to the previous record and suppress printing when they are equal.
If you use GROUP BY, output rows are sorted according to the GROUP BY columns as if you had an ORDER BY for the same columns. To avoid the overhead of sorting that GROUP BY produces, add ORDER BY NULL:
SELECT a, COUNT(b) FROM test_table GROUP BY a ORDER BY NULL;
Relying on implicit GROUP BY sorting in MySQL 5.6 is deprecated. To achieve a specific sort order of grouped results, it is preferable to use an explicit ORDER BY clause. GROUP BY sorting is a MySQL extension that may change in a future release; for example, to make it possible for the optimizer to order groupings in whatever manner it deems most efficient and to avoid the sorting overhead.
For full information - http://academy.comingweek.com/sql-groupby-clause/
SQL GROUP BY STATEMENT
SQL GROUP BY clause is used in collaboration with the SELECT statement to arrange identical data into groups.
Syntax:
1. SELECT column_nm, aggregate_function(column_nm) FROM table_nm WHERE column_nm operator value GROUP BY column_nm;
Example :
To understand the GROUP BY clauserefer the sample database.Below table showing fields from “order” table:
1. |EMPORD_ID|employee1ID|customerID|shippers_ID|
Below table showing fields from “shipper” table:
1. | shippers_ID| shippers_Name |
Below table showing fields from “table_emp1” table:
1. | employee1ID| first1_nm | last1_nm |
Example :
To find the number of orders sent by each shipper.
1. SELECT shipper.shippers_Name, COUNT (orders.EMPORD_ID) AS No_of_orders FROM orders LEFT JOIN shipper ON orders.shippers_ID = shipper.shippers_ID GROUP BY shippers_Name;
1. | shippers_Name | No_of_orders |
Example :
To use GROUP BY statement on more than one column.
1. SELECT shipper.shippers_Name, table_emp1.last1_nm, COUNT (orders.EMPORD_ID) AS No_of_orders FROM ((orders INNER JOIN shipper ON orders.shippers_ID=shipper.shippers_ID) INNER JOIN table_emp1 ON orders.employee1ID = table_emp1.employee1ID)
2. GROUP BY shippers_Name,last1_nm;
| shippers_Name | last1_nm |No_of_orders |
for more clarification refer my link
http://academy.comingweek.com/sql-groupby-clause/