I have several tables where a field is for priority (1 to 5). Problem here is that different projects have been using 5 as highest and some 1 for highest and I going to harmonize this.
My easy option is to create a temp table and copy the data over and switch as this table:
1 -> 5
2 -> 4
3 -> 3
4 -> 2
5 -> 1
I'm not that good with SQL but it feels that there should be an easy way to switch those values right off with an statement but I do have concerns of when there are huge amount of data and if something goes wrong half way then the data will be in a mess.
Should I just go with my temp table solution or should do you have a nice way of doing this straight in SQL? (Oracle 10g is being used)
Many thanks!
simply update the second table like this, a temp table is not needed because you are just reversing the priority:
update table_2
set priority = 6-priority;
You can use a CASE statement
case PRIORITY
when 5 then 1
when 4 then 2
when 3 then 3
when 2 then 4
when 1 then 5
else PRIORITY
end
Edit: texBlues' solution is much better, but I leave this here for cases where the maths isn't as neat.
To be sure that no 'mess' results if the update goes awry, use a transaction. Building on tekBlues solution (+1 for this).
START TRANSACTION;
update table_2
set priority = 6-priority;
...
COMMIT;
This is especially valid if you want to update multiple tables in one go. Single statements are implicitely handled, as hainstech pointed out in his comment correctly.
Related
I´m currently working stuck on a SQL issue (well, mainly because I can´t find a way to google it and my SQL skills do not suffice to solve it myself)
I´m working on a system where documents are edited. If the editing process is finished, users mark the document as solved. In the MSSQL database, the corresponding row is not updated but instead, a new row is inserted. Thus, every document that has been processed has [e.g.: should have] multiple rows in the DB.
See the following situation:
ID
ID2
AnotherCondition
Steps
Process
Solved
1
1
yes
Three
ATAT
AF
2
2
yes
One
ATAT
FR
2
3
yes
One
ATAT
EG
2
4
yes
One
ATAT
AF
3
5
no
One
ABAT
AF
4
6
yes
One
ATAT
FR
5
7
no
One
AVAT
EG
6
8
yes
Two
SATT
FR
6
9
yes
Two
SATT
EG
6
10
yes
Two
SATT
AF
I need to select the rows which have not been processed yet. A "processed" document has a "FR" in the "Solved" column. Sadly other versions of the document exist in the DB, with other codes in the "Solved" columns.
Now: If there is a row which has "FR" in the "Solved" column I need to remove every row with the same ID from my SELECT statement as well. Is this doable?
In order to achieve this, I have to remove the rows with the IDs 2 | 4 (because the system sadly isn´t too reliable I guess) | and 6 in my select statement. Is this possible in general?
What I could do is to filter out the duplicates afterwards, in python/js/whatever. But I am curious whether I can "remove" these rows directly in the SQL statement as well.
To rephrase it another time: How can I make a select statement which returns only (in this example) the rows containing the ID´s 1, 3 and 5?
If you need to delete all rows where every id doesn't have any "Solved = 'no'", you can use a DELETE statement that will exclude all "id" values that have at least one "Solved = 'no'" in the corresponding rows.
DELETE FROM tab
WHERE id NOT IN (SELECT id FROM tab WHERE Solved1 = 'no');
Check the demo here.
Edit. If you need to use a SELECT statement, you can simply reverse the condition in the subquery:
SELECT *
FROM tab
WHERE id NOT IN (SELECT id FROM tab WHERE Solved1 = 'yes');
Check the demo here.
I'm not sure I understand your question correct:
...every document that has been processed has [...] multiple rows in the DB
I need to find out which documents have not been processed yet
So it seems you need to find unique documents with no versions, this could be done using a GROUP BY with a HAVING clause:
SELECT
Id
FROM dbo.TableName
GROUP BY Id
HAVING COUNT(*) = 1
For my application I have a table with these three columns: user, item, value
Here's some sample data:
user item value
---------------------
1 1 50
1 2 45
1 23 35
2 1 88
2 23 44
3 2 12
3 1 27
3 5 76
3 23 44
What I need to do is, for a given user, perform simple arithmetic against everyone else's values.
Let's say I want to compare user 1 against everyone else. The calculation looks something like this:
first_user second_user result
1 2 SUM(ABS(50-88) + ABS(35-44))
1 3 SUM(ABS(50-27) + ABS(45-12) + ABS(35-44))
This is currently the bottleneck in my program. For example, many of my queries are starting to take 500+ milliseconds, with this algorithm taking around 95% of the time.
I have many rows in my database and it is O(n^2) (it has to compare all of user 1's values against everyone else's matching values)
I believe I have only two options for how to make this more efficient. First, I could cache the results. But the resulting table would be huge because of the NxN space required, and the values need to be relatively fresh.
The second way is to make the algorithm much quicker. I searched for "postgres SIMD" because I think SIMD sounds like the perfect solution to optimize this. I found a couple related links like this and this, but I'm not sure if they apply here. Also, they seem to both be around 5 years old and relatively unmaintained.
Does Postgres have support for this sort of feature? Where you can "vectorize" a column or possibly import or enable some extension or feature to allow you to quickly perform these sorts of basic arithmetic operations against many rows?
I'm not sure where you get O(n^2) for this. You need to look up the rows for user 1 and then read the data for everyone else. Assuming there are few items and many users, this would be essentially O(n), where "n" is the number of rows in the table.
The query could be phrased as:
select t1.user, t.user, sum(abs(t.value - t1.value))
from t left join
t t1
on t1.item = t.item and
t1.user <> t.user and
t1.user = 1
group by t1.user, t.user;
For this query, you want an index on t(item, user, value).
I'm trying to create a query that will insert new records to a table or update already existing records, but I'm getting stuck on the filtering and grouping for the criteria I want.
I have two tables: tbl_PartInfo, and dbo_CUST_BOOK_LINE.
I'm want to select from dbo_CUST_BOOK_LINE based upon the combination of CUST_ORDER_ID, CUST_ORDER_LINE_NO, and REVISION_ID. Each customer order can have multiple lines, and each line can have multiple revision. I'm trying to select the unique combinations of each order and it's connected lines, but take the connected information for the row with the highest value in the revision column.
I want to insert/update from dbo_CUST_BOOK_LINE the following columns:
CUST_ORDER_ID
PART_ID
USER_ORDER_QTY
UNIT_PRICE
I want to insert/update them into tbl_PartInfo as the following columns respectively:
JobID
DrawingNumber
Quantity
UnitPrice
So if I have the following rows in dbo_CUST_BOOK_LINE (PART_ID omitted for example)
CUST_ORDER_ID CUST_ORDER_LINE_NO REVISION_ID USER_ORDER_QTY UNIT_PRICE
SCabc 1 1 0 100
SCabc 1 2 4 150
SCabc 1 3 4 125
SCabc 2 3 2 200
SCxyz 1 1 0 0
SCxyz 1 2 3 50
It would return
CUST_ORDER_ID CUST_ORDER_LINE_NO (REVISION_ID) USER_ORDER_QTY UNIT_PRICE
SCabc 1 3 4 125
SCabc 2 3 2 200
SCxyz 1 2 3 50
but with PART_ID included and without REVISION_ID
So far, my code is just for the inset portion as I was trying to get the correct records selected, but I keep getting duplicates of CUST_ORDER_ID and CUST_ORDER_LINE_NO.
INSERT INTO tbl_PartInfo ( JobID, DrawingNumber, Quantity, UnitPrice, ProductFamily, ProductCategory )
SELECT dbo_CUST_BOOK_LINE.CUST_ORDER_ID, dbo_CUST_BOOK_LINE.PART_ID, dbo_CUST_BOOK_LINE.USER_ORDER_QTY, dbo_CUST_BOOK_LINE.UNIT_PRICE, dbo_CUST_BOOK_LINE.CUST_ORDER_LINE_NO, Max(dbo_CUST_BOOK_LINE.REVISION_ID) AS MaxOfREVISION_ID
FROM dbo_CUST_BOOK_LINE, tbl_PartInfo
GROUP BY dbo_CUST_BOOK_LINE.CUST_ORDER_ID, dbo_CUST_BOOK_LINE.PART_ID, dbo_CUST_BOOK_LINE.USER_ORDER_QTY, dbo_CUST_BOOK_LINE.UNIT_PRICE, dbo_CUST_BOOK_LINE.CUST_ORDER_LINE_NO;
This has been far more complicated that anything I've done so far, so any help would be greatly appreciated. Sorry about the long column names, I didn't get to choose them.
I did some research and think I found a way to make it work, but I'm still testing it. Right now I'm using three queries, but it should be easily simplified into two when complete.
The first is an append query that takes the two columns I want to get distinct combo's from and selects them and using "group by," while also selecting max of the revision column. It appends them to another table that I'm using called tbl_TempDrop. This table is only being used right now to reduce the number of results before the next part.
The second is an update query that updates tbl_TempDrop to include all the other columns I wanted by setting the criteria equal to the three selected columns from the first query. This took an EXTREMELY long time to complete when I had 700,000 records to work with, hence the use of the tbl_TempDrop.
The third query is a basic append query that appends the rows of tbl_TempDrop to the end destination, tbl_PartInfo.
All that's left is to run all three in a row.
I didn't want to include the full details of any tables or queries yet until I ensure that it works as desired, and because some of the names are vague since I will be using this method for multiple query searches.
This website helped me a little to make sure I had the basic idea down. http://www.techonthenet.com/access/queries/max_query2_2007.php
Let me know if you see any flaws with the ideology!
I have a table in the form:
date / category (string) / count (integer)
--------------------------------------------
7/15 A 3
7/15 B 7
7/15 C 2
7/16 A 9
7/16 B 1
7/16 C 2
Basically, for each day, each category will have a count associated with it.
The problem is, I don't necessarily know what these categories will end up being. Say I know they are A, B, and C, but next week, there is a D, E, and F.
And this is the view that I want to build:
Date / A / B / C / .. (however many categories found)
---------------------------------------------------------
7/15 3 5 2 3 4
7/16 9 5 9 6 4
...
..
.
I usually know enough SQL to get by, but this one is racking my brain. I don't think I am using the right vocabulary when trying to google it, because I'm not finding the answers I am looking for.
The answer is simple, you cannot build a view to do what you would like. A view has its columns pre-defined.
You could do one of the following:
Create a stored procedure that creates a view every week. This stored procedure would analyze the data, determine the columns, and then use dynamic SQL to alter the view.
Change the definition of what you want and put the values in a single column, separated by commas (or some other character).
Predefine a list of acceptable columns, create the view (using pivot, say) and then periodically go through an modify it when new values arise.
Do the pivoting at the application layer. This is particularly easy in Excel.
One big caveat with (1) and (3). If anything uses the view as "select * from view", you need to be sure that those queries/stored procedures/user defined functions/etc. are recompiled. Otherwise, they will have the wrong list of columns (this may only apply to SQL Server).
I have the following tables, the groups table which contains hierarchically ordered groups and group_member which stores which groups a user belongs to.
groups
---------
id
parent_id
name
group_member
---------
id
group_id
user_id
ID PARENT_ID NAME
---------------------------
1 NULL Cerebra
2 1 CATS
3 2 CATS 2.0
4 1 Cerepedia
5 4 Cerepedia 2.0
6 1 CMS
ID GROUP_ID USER_ID
---------------------------
1 1 3
2 1 4
3 1 5
4 2 7
5 2 6
6 4 6
7 5 12
8 4 9
9 1 10
I want to retrieve the visible groups for a given user. That it is to say groups a user belongs to and children of these groups. For example, with the above data:
USER VISIBLE_GROUPS
9 4, 5
3 1,2,4,5,6
12 5
I am getting these values using recursion and several database queries. But I would like to know if it is possible to do this with a single SQL query to improve my app performance. I am using MySQL.
Two things come to mind:
1 - You can repeatedly outer-join the table to itself to recursively walk up your tree, as in:
SELECT *
FROM
MY_GROUPS MG1
,MY_GROUPS MG2
,MY_GROUPS MG3
,MY_GROUPS MG4
,MY_GROUPS MG5
,MY_GROUP_MEMBERS MGM
WHERE MG1.PARENT_ID = MG2.UNIQID (+)
AND MG1.UNIQID = MGM.GROUP_ID (+)
AND MG2.PARENT_ID = MG3.UNIQID (+)
AND MG3.PARENT_ID = MG4.UNIQID (+)
AND MG4.PARENT_ID = MG5.UNIQID (+)
AND MGM.USER_ID = 9
That's gonna give you results like this:
UNIQID PARENT_ID NAME UNIQID_1 PARENT_ID_1 NAME_1 UNIQID_2 PARENT_ID_2 NAME_2 UNIQID_3 PARENT_ID_3 NAME_3 UNIQID_4 PARENT_ID_4 NAME_4 UNIQID_5 GROUP_ID USER_ID
4 2 Cerepedia 2 1 CATS 1 null Cerebra null null null null null null 8 4 9
The limit here is that you must add a new join for each "level" you want to walk up the tree. If your tree has less than, say, 20 levels, then you could probably get away with it by creating a view that showed 20 levels from every user.
2 - The only other approach that I know of is to create a recursive database function, and call that from code. You'll still have some lookup overhead that way (i.e., your # of queries will still be equal to the # of levels you are walking on the tree), but overall it should be faster since it's all taking place within the database.
I'm not sure about MySql, but in Oracle, such a function would be similar to this one (you'll have to change the table and field names; I'm just copying something I did in the past):
CREATE OR REPLACE FUNCTION GoUpLevel(WO_ID INTEGER, UPLEVEL INTEGER) RETURN INTEGER
IS
BEGIN
DECLARE
iResult INTEGER;
iParent INTEGER;
BEGIN
IF UPLEVEL <= 0 THEN
iResult := WO_ID;
ELSE
SELECT PARENT_ID
INTO iParent
FROM WOTREE
WHERE ID = WO_ID;
iResult := GoUpLevel(iParent,UPLEVEL-1); --recursive
END;
RETURN iResult;
EXCEPTION WHEN NO_DATA_FOUND THEN
RETURN NULL;
END;
END GoUpLevel;
/
Joe Cleko's books "SQL for Smarties" and "Trees and Hierarchies in SQL for Smarties" describe methods that avoid recursion entirely, by using nested sets. That complicates the updating, but makes other queries (that would normally need recursion) comparatively straightforward. There are some examples in this article written by Joe back in 1996.
I don't think that this can be accomplished without using recursion. You can accomplish it with with a single stored procedure using mySQL, but recursion is not allowed in stored procedures by default. This article has information about how to enable recursion. I'm not certain about how much impact this would have on performance verses the multiple query approach. mySQL may do some optimization of stored procedures, but otherwise I would expect the performance to be similar.
Didn't know if you had a Users table, so I get the list via the User_ID's stored in the Group_Member table...
SELECT GroupUsers.User_ID,
(
SELECT
STUFF((SELECT ',' +
Cast(Group_ID As Varchar(10))
FROM Group_Member Member (nolock)
WHERE Member.User_ID=GroupUsers.User_ID
FOR XML PATH('')),1,1,'')
) As Groups
FROM (SELECT User_ID FROM Group_Member GROUP BY User_ID) GroupUsers
That returns:
User_ID Groups
3 1
4 1
5 1
6 2,4
7 2
9 4
10 1
12 5
Which seems right according to the data in your table. But doesn't match up with your expected value list (e.g. User 9 is only in one group in your table data but you show it in the results as belonging to two)
EDIT: Dang. Just noticed that you're using MySQL. My solution was for SQL Server. Sorry.
-- Kevin Fairchild
There was already similar question raised.
Here is my answer (a bit edited):
I am not sure I understand correctly your question, but this could work My take on trees in SQL.
Linked post described method of storing tree in database -- PostgreSQL in that case -- but the method is clear enough, so it can be adopted easily for any database.
With this method you can easy update all the nodes depend on modified node K with about N simple SELECTs queries where N is distance of K from root node.
Good Luck!
I don't remember which SO question I found the link under, but this article on sitepoint.com (second page) shows another way of storing hierarchical trees in a table that makes it easy to find all child nodes, or the path to the top, things like that. Good explanation with example code.
PS. Newish to StackOverflow, is the above ok as an answer, or should it really have been a comment on the question since it's just a pointer to a different solution (not exactly answering the question itself)?
There's no way to do this in the SQL standard, but you can usually find vendor-specific extensions, e.g., CONNECT BY in Oracle.
UPDATE: As the comments point out, this was added in SQL 99.