I have a table with data similar to:
Inven DESCRIPT PrintOrder
---------------------------------
1 D 9
2 B 0
3 A 5
4 Z 0
5 X 1
. . .
. . .
. . .
I would like to sort the table on column DESCRIPT descending alpha (A - Z) and then update the column PRINTORDER so that when done, the record with PRINTORDER = 1 is the the highest alpha (A) and the record with the highest value for PRINTORDER will be the lowest in alpha (Z).
Is this possible without using temporary columns? Not a deal breaker if not, just a preference.
DESIRED RESULT:
To update the PrintOrder values based on the sorting result
Inven DESCRIPT PrintOrder
---------------------------------
1 D 3
2 B 2
3 A 1
4 Z 5
5 X 4
I am unclear whether you want to modify the table or just create a result set. Here is the solution to the latter using standard SQL:
select Inven, Descript, row_number() over (order by Descript) as PrintOrder
from table t
order by Descript;
EDIT:
In MySQL, the select would look like:
select t.*
from (select Inven, Descript, (#rn := #rn + 1) as PrintOrder
from table t cross join (select #rn := 0) params
order by Descript
) t
order by Inven;
The update is slightly trickier, because you cannot sort and initialize a variable:
update t
set PrintOrder = (#rn := coalesce(#rn + 1, 1))
order by Descript;
This should do it:
Update T
set PRINTORDER = ASCII(UPPER(DESCRIPT)) - 64
while the ASCII of A is 65 in your system. :)
EDIT:
As you said there might be something more, so we need to change it a bit by assuming you have a PK column name as Id:
UPDATE T
set PRINTORDER = T2.Order
FROM T
INNER JOIN (SELECT IDENTITY(int, 1,1) AS Order,Id FROM T Order By DESCRIPT ASC) T2 ON T.Id=T2.Id
But in this way even two record has same DESCRIPT would end up have different printorder, it could be a bit more complex if you want keep them the same.
EDIT:
Sorry just realized you are using MySql, the IDENTITY(int, 1,1) is from SQL Server, basically it generate a row number, you might need something different to have one: http://blog.sqlauthority.com/2014/03/08/mysql-generating-row-number-for-each-row-using-variable/
After arriving at my office, and chatting with my colleague, the question posed is completely inaccurate. So I'll close this thread, and an open a new one with a more accurate description of the issue.
Thank you Gordon & Simon for your responses, they are most appreciated.
Related
Hello I've got a question, how (if it possible), I can create new datatables with close same rows but if In column value is in string "/" for example
ID
column_param
column_sym
column_value
column_val2
First
param_test1
ABC
11/12
test
Second
param_test2
CDE
22/11
test
Third
param_test3
EFG
44
teste
4'th
param_test4
HIJ
33/22
test
And here if I have param_test1 and param_test4 and if in this column value has "/" I want to create 2 other rows but if I will not set param_test2 then it stay as it is and everything should be in new datatable. Is any way to create this?
Thank you in advance.
Expected result:
As per Gordon's answer, I'm not sure what should be done with the your ID column.
I've replaced these with row numbers.
Depending on your version of MySQL/MariaDB, the ROW_NUMBER() window function may not be available. Depending on whether IDs in the output are necessary you may be able to simply omit this.
I've assumed the existence of a table called myNumbers which contains a single field num and is populated with positive integers from 1 to whatever you're likely to need.
I've included more in the output that you asked for, which will hopefully help you understand what's going on
SELECT
ROW_NUMBER() OVER (ORDER BY d.ID, n.num) as NewID,
d.ID as OriginalID,
n.num as,
d.column_param,
d.column_sym,
d.column_value as orig_value,
CASE WHEN column_param = 'param_test2' THEN d.column_value
ELSE substring_index(substring_index(d.column_value,'/',n.num),'/',-1) END as split_value,
d.column_val2
FROM
myData d
JOIN myNumbers n on char_length(d.column_value)-char_length(replace(d.column_value,'/','')) >= n.num-1
WHERE
n.num = 1 OR d.column_param <> 'param_test2'
ORDER BY
d.ID,
n.num
See this DB Fiddle (the columns output in a different order than I've specified, but I think that's a DB Fiddle quirk).
If you only want to "split" say param_test1 and param_test4 rows the code above code could be amended as follows:
SELECT
ROW_NUMBER() OVER (ORDER BY d.ID, n.num) as NewID,
d.ID as OriginalID,
d.column_param,
d.column_sym,
n.num,
d.column_value as orig_value,
CASE WHEN column_param NOT IN ('param_test1','param_test4') THEN d.column_value
ELSE substring_index(substring_index(d.column_value,'/',n.num),'/',-1) END as split_value,
d.column_val2
FROM
myData d
JOIN myNumbers n on char_length(d.column_value)-char_length(replace(d.column_value,'/','')) >= n.num-1
WHERE
n.num = 1 OR d.column_param IN ('param_test1','param_test4')
ORDER BY
d.ID,
n.num
I don't know how the id is being set, but you can do what you want using union all:
select column_param, column_sym,
substring_index(column_value, '/', 1) as column_value,
column_val2
from t
union all
select column_param, column_sym,
substring_index(column_value, '/', -1) as column_value,
column_val2
from t
where column_value = '%/%';
Couldn't really explain my problem with words, but with an example I can show it clearly:
I have a table like this:
id num val flag
0 3 10 1
1 5 12 2
2 7 12 1
3 11 15 2
And I want to go through all the rows, and calculate the increase of the "num", and multiply that difference with the "val" value. And when I calculated all of these, I want to add these results together, but grouped based on the "flag" values.
This is the mathematical equation, that I want to run on the table:
Result_1 = (3-0)*10 + (7-3)*12
Result_2 = (5-0)*12 + (11-5)*15
78 = Result_1
150 = Result_2
Thank you.
Interesting question. Unfortunately MYSQL doesn't support recursive queries, so you'll need to be a little creative here. Something like this could work:
select flag,
sum(calc)
from (
select flag,
(num-if(#prevflag=flag,#prevnum,0))*val calc,
#prevnum:=num prevnum,
#prevflag:=flag prevflag
from yourtable
join (select #prevnum := 0, #prevflag := 0) t
order by flag
) t
group by flag
SQL Fiddle Demo
The problem:
We have a number of entries within a table but we are only interested in the ones that appear in a given sequence. For example we are looking for three specific "GFTitle" entries ('Pearson Grafton','Woolworths (P and O)','QRX - Brisbane'), however they have to appear in a particular order to be considered a valid route. (See image below)
RowNum GFTitle
------------------------------
1 Pearson Grafton
2 Woolworths (P and O)
3 QRX - Brisbane
4 Pearson Grafton
5 Woolworths (P and O)
6 Pearson Grafton
7 QRX - Brisbane
8 Pearson Grafton
9 Pearson Grafton
So rows (1,2,3) satisfy this rule but rows (4,5,6) don't even though the first two entries (4,5) do.
I am sure there is a way to do this via CTE's but some help would be great.
Cheers
This is very simple using even good old tools :-) Try this quick-and-dirty solution, assuming your table name is GFTitles and RowNumber values are sequential:
SELECT a.[RowNum]
,a.[GFTitle]
,b.[GFTitle]
,c.[GFTitle]
FROM [dbo].[GFTitles] as a
join [dbo].[GFTitles] as b on b.RowNumber = a.RowNumber + 1
join [dbo].[GFTitles] as c on c.RowNumber = a.RowNumber + 2
WHERE a.[GFTitle] = 'Pearson Grafton' and
b.[GFTitle] = 'Woolworths (P and O)' and
c.[GFTitle] = 'QRX - Brisbane'
Assuming RowNum has neither duplicates nor gaps, you could try the following method.
Assign row numbers to the sought sequence's items and join the row set to your table on GFTitle.
For every match, calculate the difference between your table's row number and that of the sequence. If there's a matching sequence in your table, the corresponding rows' RowNum differences will be identical.
Count the rows per difference and return only those where the count matches the number of sequence items.
Here's a query that implements the above logic:
WITH SoughtSequence AS (
SELECT *
FROM (
VALUES
(1, 'Pearson Grafton'),
(2, 'Woolworths (P and O)'),
(3, 'QRX - Brisbane')
) x (RowNum, GFTitle)
)
, joined AS (
SELECT
t.*,
SequenceLength = COUNT(*) OVER (PARTITION BY t.RowNum - ss.RowNum)
FROM atable t
INNER JOIN SoughtSequence ss
ON t.GFTitle = ss.GFTitle
)
SELECT
RowNum,
GFTitle
FROM joined
WHERE SequenceLength = (SELECT COUNT(*) FROM SoughtSequence)
;
You can try it at SQL Fiddle too.
I have a query problem about retrieving number of rows that the counting will start from the specified row. These are the row values on my MySQL database.
John Parker
Tony Graham
Perter Smith
Annabelle Sergio
Kris Pata
Neshren Luca
Paul Pon
Zervich Nuckrav
Allan Paulson
Imanu Hashmarida
Varick Dagovich
Senster Burgsman
Lito Umani
Ramsay Nudillo
Now I want to retrieve the first 5 row that will start from Neshren Luca so that the resultset may look like this:
Neshren Luca
Paul Pon
Zervich Nuckrav
Allan Paulson
Imanu Hashmarida
How may I do that?
Note: I will not try to retrieve the row values base on number of row but base from a specific row value.
This looks very ugly but have this a try, this uses local variable
SET #selectedName := 'Neshren Luca'; -- set the name here
SET #selectRow :=
(
SELECT RankNo
FROM
(
SELECT #rowNum := #rowNum + 1 AS RankNo,
a.Names
FROM tableName a, (SELECT #rowNum:= 0) b
) x
WHERE Names = #selectedName
);
SELECT Names
FROM
(
SELECT #rowNum1 := #rowNum1 + 1 AS RankNo, a.Names
FROM tableName a, (SELECT #rowNum1:= 0) b
) x
WHERE RankNo BETWEEN #selectRow AND #selectRow + 4
SQLFiddle Demo
Looks like the above select statement will work fine for that..other wise you have to do other way but it will bit lengthy..that..
-> You have to get the above records into a cursor
-> Looping through the cursor and getting the records..
SQL engine may have some 'natural' row order, but it is not guaranteed. You should have primary key, say ID, then ORDER BY ID, find first ID WHERE your string is. And then select first N items WHERE ID >= that id.
Edit: Or, if your database guarantees natural order, find row id/index and LIMIT/OFFSET by this value. SQLite has built-in natural rowid for each table row, for example.
*Hey everyone, I am working on a query and am unsure how to make it process as quickly as possible and with as little redundancy as possible. I am really hoping someone there can help me come up with a good way of doing this.
Thanks in advance for the help!*
Okay, so here is what I have as best I can explain it. I have simplified the tables and math to just get across what I am trying to understand.
Basically I have a smallish table that never changes and will always only have 50k records like this:
Values_Table
ID Value1 Value2
1 2 7
2 2 7.2
3 3 7.5
4 33 10
….50000 44 17.2
And a couple tables that constantly change and are rather large, eg a potential of up to 5 million records:
Flags_Table
Index Flag1 Type
1 0 0
2 0 1
3 1 0
4 1 1
….5,000,000 1 1
Users_Table
Index Name ASSOCIATED_ID
1 John 1
2 John 1
3 Paul 3
4 Paul 3
….5,000,000 Richard 2
I need to tie all 3 tables together. The most results that are likely to ever be returned from the small table is somewhere in the neighborhood of 100 results. The large tables are joined on the index and these are then joined to the Values_Table ON Values_Table.ID = Users_Table.ASSOCIATED_ID …. That part is easy enough.
Where it gets tricky for me is that I need to return, as quickly as possible, a list limited to 10 results where value1 and value2 are mathematically operated on to return a new_ value where that new_value is less than 10 and the result is sorted by that new_value and any other where statements I need can be applied to the flags. I do need to be able to move along the limit. EG LIMIT 0,10 / 11,10 / 21,10 etc...
In a subsequent (or the same if possible) query I need to get the top 10 count of all types that matched that criteria before the limit was applied.
So for example I want to join all of these and return anything where Value1 + Value2 < 10 AND I also need the count.
So what I want is:
Index Name Flag1 New_Value
1 John 0 9
2 John 0 9
5000000 Richard 1 9.2
The second response would be:
ID (not index) Count
1 2
2 1
I tried this a few ways and ultimately came up with the following somewhat ugly query:
SELECT INDEX, NAME, Flag1, (Value1 * some_variable + Value2) as New_Value
FROM Values_Table
JOIN Users_Table ON ASSOCIATED_ID = ID
JOIN Flags_Table ON Flags_Table.Index = Users_Table.Index
WHERE (Value1 * some_variable + Value1) < 10
ORDER BY New_Value
LIMIT 0,10
And then for the count:
SELECT ID, COUNT(TYPE) as Count, (Value1 * some_variable + Value2) as New_Value
FROM Values_Table
JOIN Users_Table ON ASSOCIATED_ID = ID
JOIN Flags_Table ON Flags_Table.Index = Users_Table.Index
WHERE (Value1 * some_variable + Value1) < 10
GROUP BY TYPE
ORDER BY New_Value
LIMIT 0,10
Being able to filter on the different flags and such in my WHERE clause is important; that may sound stupid to comment on but I mention that because from what I could see a quicker method would have been to use the HAVING statement but I don't believe that will work in certain instance depending on what I want to use my WHERE clause to filter against.
And when filtering using the flags table :
SELECT INDEX, NAME, Flag1, (Value1 * some_variable + Value2) as New_Value
FROM Values_Table
JOIN Users_Table ON ASSOCIATED_ID = ID
JOIN Flags_Table ON Flags_Table.Index = Users_Table.Index
WHERE (Value1 * some_variable + Value1) < 10 AND Flag1 = 0
ORDER BY New_Value
LIMIT 0,10
...filtered count:
SELECT ID, COUNT(TYPE) as Count, (Value1 * some_variable + Value2) as New_Value
FROM Values_Table
JOIN Users_Table ON ASSOCIATED_ID = ID
JOIN Flags_Table ON Flags_Table.Index = Users_Table.Index
WHERE (Value1 * some_variable + Value1) < 10 AND Flag1 = 0
GROUP BY TYPE
ORDER BY New_Value
LIMIT 0,10
That works fine but has to run the math multiple times for each row, and I get the nagging feeling that it is also running the math multiple times on the same row in the Values_table table. My thought was that I should just get only the valid responses from the Values_table first and then join those to the other tables to cut down on the processing; with how SQL optimizes things though I wasn't sure if it might not already be doing that. I know I could use a HAVING clause to only run the math once if I did it that way but I am uncertain how I would then best join things.
My questions are:
Can I avoid running that math twice and still make the query work
(or I suppose if there is a good way
to make the first one work as well
that would be great)
What is the fastest way to do this
as this is something that will
be running very often.
It seems like this should be painfully simple but I am just missing something stupid.
I contemplated pulling into a temp table then joining that table to itself but that seems like I would trade math for iterations against the table and still end up slow.
Thank you all for your help in this and please let me know if I need to clarify anything here!
** To clarify on a question, I can't use a 3rd column with the values pre-calculated because in reality the math is much more complex then addition, I just simplified it for illustration's sake.
Do you have a benchmark query to compare against? Usually it doesn't work to try to outsmart the optimizer. If you have acceptable performance from a starting query, then you can see where extra work is being expended (indicated by disk reads, cache consumption, etc.) and focus on that.
Avoid the temptation to break it into pieces and solve those. That's an antipattern. That includes temp tables especially.
Redundant math is usually ok - what hurts is disk activity. I've never seen a query that needed CPU work reduction on pure calculations.
Gather your results and put them in a temp table
SELECT * into TempTable FROM (SELECT INDEX, NAME, Type, ID, Flag1, (Value1 + Value2) as New_Value
FROM Values_Table
JOIN Users_Table ON ASSOCIATED_ID = ID
JOIN Flags_Table ON Flags_Table.Index = Users_Table.Index
WHERE New_Value < 10)
ORDER BY New_Value
LIMIT 0,10
Return Result for First Query
SELECT INDEX, NAME, Flag1, New_Value
FROM TempTable
Return Results for count of Types
Select ID, Count(Type)
FROM TempTable
GROUP BY TYPE
Is there any chance that you can add a third column to the values_table with the pre-calculated value? Even if the result of your calculation is dependent on other variables, you could run the calculation for the whole table but only when those variables change.