I am trying to solve a business flow issue at my work and I have an idea that I hope is technically feasible in SQL. What I would like to try and do is store different formulas in SQL syntax into database columns. Within SQL queries I would set variables to equal these columns so that the content of the columns is parsed as a part of the query and the different SQL statements pops up depending on the select specifications.
Short and sweet: I have some widgets to sell and whether or not a client can get these widgets depends on what other widgets they have bought, should have and shouldn’t have, country, customerid, their widget version, widget category and a couple of other things.
My question is how would someone proceed with this? I’m sure someone has made a similar setup before but which methods would be useful to study for my case? Are there case studies where I can find inspiration? I have searched for this without any luck. Hopefully someone who have solved similair issues before would be able to point me in a direction.
Thanks to whom‘ever is able to answer and has had the interest to read my post.
Best regards
Zaid
**OK this is more of a comment than an answer but the formatting doesn't work if I enter it as a comment!
To very vaguely answer your question I would have a Widgets table ie
WidgetID | Widget Name
1 Widget1
2 Widget2
3 Widget3
4 Widget4
Then have a WidgetRequirements table which is
WidgetRequiredID | WidgetID | RequiredWidgetID
1 1 2
2 1 3
3 1 4
4 2 4
5 3 1
6 3 4
This tells you that WidgetID 1 needs Widgets 2, 3 and 4 in order to be "active".
Widget 2 only needs widget4 to be active and Widget3 needs widgets 1 and 4.
This should get you started, expand on this theory.
I know this question has been asked and answered. I understand the problem and I understand the underlying cause and I understand the solution. What I DON'T understand is how to implement the solution.
I'll try to be detailed....
Background: Each material is being grouped on WellID (I work in oil and gas) and SandType which is my primary key in each table, these come from 2 lookup tables one for each. (I work in oil and gas)
I have 3 tables that store material (sand)) weights at 3 different stages in the job process. Basically the weight from the engineer's DESIGN, what was DELIVERED and what is in INVENTORY.
I know that the join is messed up and adding the total for each row in each table. Sometimes double triple etc.
I am grouping on WellID and SandID.
Now I don't want someone to do the work for me. I just don't know how or where in access to restrict it to what I want, or if modifying t he sql the proper way to write the code. Current work around is 3 separate sum queries one for each table, but that is going to get inefficient and added steps.
My whole database purpose and subsequent reports hinge off math on these 3 numbers so, my show stopper here is putting the fat lady on stage, and is about to become a deal breaker at the end of the line! 0
I need some advice, direction, criticism, wisdom, witty euphemisms or a new job!
The 3 tables look as follows
Design:
T_DESIGN
DesignID WellID Sand_ID Weight_DES Time_DES
89 201 1 100 4/21/2014 6:46:02 AM
98 201 2 100 4/21/2014 7:01:22 AM
86 201 4 100 4/21/2014 6:28:01 AM
93 228 5 100 4/21/2014 6:53:34 AM
91 228 1 100 4/21/2014 6:51:23 AM
92 228 1 100 4/21/2014 6:53:30 AM
Delivered:
T_BOL
BOLID WellID_BOL SandID_BOL Weight_BOL
279 201 1 100
280 201 1 100
281 228 2 5
282 228 1 10
283 228 9 100
Inventory:
T_BIN
StrapID WellID_BIN SandID_BIN Weight_BIN
11 201 1 100
13 228 1 10
14 228 1 0
17 228 1 103
19 201 1 50
The Query Results:
Test Query99
WellID
WellID SandID Sum Of Weight_DES Sum Of Weight_BOL Sum Of Weight_BIN
201 1 400 400 300
228 1 600 60 226
SQL:
SELECT DISTINCTROW L_WELL.WellID, L_SAND.SandID,
Sum(T_DESIGN.Weight_DES) AS [Sum Of Weight_DES],
Sum(T_BOL.Weight_BOL) AS [Sum Of Weight_BOL],
Sum(T_BIN.Weight_BIN) AS [Sum Of Weight_BIN]
FROM ((L_SAND INNER JOIN
(L_WELL INNER JOIN T_DESIGN ON L_WELL.[WellID] = T_DESIGN.[WellID_DES])
ON L_SAND.SandID = T_DESIGN.[SandID_DES])
INNER JOIN T_BIN
ON (L_WELL.WellID = T_BIN.WellID_BIN)
AND (L_SAND.SandID = T_BIN.SandID_BIN))
INNER JOIN T_BOL
ON (L_WELL.WellID = T_BOL.WellID_BOL) AND (L_SAND.SandID = T_BOL.SandID_BOL)
GROUP BY L_WELL.WellID, L_SAND.SandID;
Two LooUp tables are for Well Names and Sand Types. (Well has been abbreviate do to size)
L_Well:
WellID WellName_WELL
3 AAGVIK 1-35H
4 AARON 1-22
5 ACHILLES 5301 41-12B
6 ACKLINS 6092 12-18H
7 ADDY 5992 43-21 #1H
8 AERABELLE 5502 43-7T
9 AGNES 1-13H
10 AL 5493 44-23B
11 ALDER 6092 43-8H
12 AMELIA FEDERAL 5201 41-11B
13 AMERADA STATE 1-16X
14 ANDERSMADSON 5201 41-13H
15 ANDERSON 1-13H
16 ANDERSON 7-18H
17 ANDRE 5501 13-4H
18 ANDRE 5501 14-5 3B
19 ANDRE SHEPHERD 5501 14-7 1T
Sand Lookup:
LSand
SandID SandType_Sand
1 100 Mesh
2 20/40 EP
3 20/40 RC
4 20/40 W
5 30/50 Ceramic
6 30/50 EP
7 30/50 RC
8 40/70 EP
9 40/70 W
10 NA See Notes
Querying and Joining Aggregation Data through an MS Access Database
I noticed your concern for pointers on how to implement some of the theory behind your aggregation queries. While SQL queries are good power-tools to get to the core of a difficult analysis problem, it might also be useful to show some of the steps on how to bring things together using the built-in design tools of MS Access.
This solution was developed on MS Access 2010.
Comments on Previous Solutions
#xQbert had a solid start with the following SQL statement. The sub query approach could be visualized as individual query objects created in Access:
FROM
(SELECT WellID, Sand_ID, Sum(weight_DES) as sumWeightDES
FROM T_DESGN) A
INNER JOIN
(SELECT WellID_BOL, Sum(Weight_BOL) as SUMWEIGHTBOL
FROM T_BOL B) B
ON A.Well_ID = B.WellID_BOL
INNER JOIN
(SELECT WellID_BIN, sum(Weight_Bin) as SumWeightBin
FROM T_BIN) C
ON C.Well_ID_BIN = B.Well_ID_BOL
Depending on the actual rules of the business data, the following assumptions made in this query may not necessarily be true:
Will the tables of T_DESIGN, T_BOL and T_BIN be populated at the same time? The sample data has mixed values, i.e., there are WellID and SandID combinations which do not have values for all three of these categories.
INNER type joins assume all three tables have records for each dimension value (Well-Sand combination)
#Frazz improved on the query design by suggesting that whatever is selected as the "base" joining table (T_DESIGN in this case), this table must be populated with all the relevant dimensional values (WellID and SandID combinations).
SELECT
WellID_DES AS WellID,
SandID_DES AS SandID,
SUM(Weight_DES) AS Weight_DES,
(SELECT SUM(Weight_BOL) FROM T_BOL WHERE T_BOL.WellID_BOL=d.WellID_DES
AND T_BOL.SandID_BOL=d.SandID_DES) AS Weight_BOL,
(SELECT SUM(Weight_BIN) FROM T_BIN WHERE T_BIN.WellID_BIN=d.WellID_DES
AND T_BIN.SandID_BIN=d.SandID_DES) AS Weight_BIN
FROM T_DESIGN;
(... note: a group-by statement should be here...)
This was animprovement because now all joins originate from a single point. If a key-value does not exist in either T_BOL or T_BIN, results will still come back and the entire record of the query would not be lost.
Again, it may be possible that there are no T_DESIGN records matching to values stored in the other tables.
Building Aggregation Sub Query Objects
The presented data does not suggest that there is any direct interaction between the data in each of the three tables aside from lining up their results in the end for presentation based on a common key-value pair (WellID and SandID). Since we are using Access, there is a chance to do these calculations separately.
This query was designed using the "summarizing" feature of the Access query design tool. It's output, after pointing to the T_DESIGN table looked like this:
Making Dimension Table Through a Cartesian Product
There are mixed opinions out there about cartesian products, but they do actually have a purpose.
Most of the concern is that a runaway cartesian product query will make millions and millions of nonsensical data values. In this query, it's specifically designed to simulate a real business condition.
The Case for a Cartesian Product
Picking from the sample data provided:
Some of the Sand Types: "20/40 EP", "30/50 Ceramic", "40/70 EP", and "30/50 RC" that are moved between their respective wells, are these sand types found at these wells consistently throughout the year?
Without an anchoring dimension for the key-values, Wells would not be found anywhere in the database via querying. It's not that they do not exist... it's just that there is no recorded data (i.e., Sand Type Weights delivered) for them.
A Reference Dimension Query Product
A dimension query is simple to produce. By referencing the two sources of keys: L_WELL and L_SAND (both look up tables or dimensional tables) without identifying a join condition, all the different combinations of the two key-values (WellID and SandID) are made:
The shortcut in SQL looks like this:
SELECT L_WELL.WellID, L_SAND.SandID, L_WELL.WellName, L_SAND.SandType
FROM L_SAND, L_WELL;
The resulting data looks like this:
Instead of using any of the operational data tables: T_DESIGN, T_BOL, or T_BIN as sources of data for a static dimension such as a list of Oil Wells, or a catalog of Sand Types, that data has been predetermined and can even be transferred to a real table since it probably will not change much once it is created.
Correlating Sub Query Results from Different Sources
After repeating the process and creating the summary tables for the other two sources (T_BOL and T_BIN), You can finally arrange the results through a simple query and join process.
The actual JOIN operations are between the dimension table/query: QSUB_WELL_SAND and all three of the summary queries: QSUB_DES, QSUB_BOL, and QSUB_BIN.
I have chosen to chosen to implement LEFT OUTER joins. If you are not sure of the difference between the different "outer" joins, this is the choice I made through the Access Query Design dialogue:
QSUB_WELL_SAND is defined as our anchor dimension. It will always have more records than any of the other tables. An OUTER JOIN should be defined to KEEP all reference dimension records... and all Summary Table query results, regardless if there is a match between the two Query results.
QSUB_WEIGHTS/ The Query to Combine All Sub Query Results
This is what the design of the final output query looks like:
This is what the data output looks like when this query design is executed:
Conclusions and Clean Up: Some Closing Thoughts
With respect to the join to the dimension query, there is a lot of empty space where there are no records or data to report on. This is where a cleverly placed filter or query criteria can shrink the output to exactly what you care to look at the most. Here's how mine looked after I added additional ending query criteria:
My data was based on what was supplied by the OP, except where the ID's assigned to the Well Type attribute did not match the sample data. The values I assigned instead are posted below as well.
Access supports a different style of database operations. Step-wise queries can be developed to hold pre-processed, special sets of data that can be reintroduced to the other data tables and query results to develop complex query criteria.
All this being said, Programming in SQL can also be just as rewarding. Be sure to explore some of the differences between the results and the capabilities you can tap into by using one approach (sql coding), the other approach (access design wizards) or both of the approaches. There's definitely a lot of room to grow and discover new capabilities from just the example provided here.
Hopefully I haven't stolen all the fun from developing a solution for your situation. I read into your comment about "building more on top" as the harbinger of more fun to come, so I don't feel so bad...! Happy Developing!
Data Modifications from the Sample Set
Without understanding L_SAND and L_WELL this is the best I could come up with..
use sub selects to get the sums first so you don't compound the data issues on the joins.
Select WellID, Sand_ID, sumWeightDES, WellID_BOL, SUMWEIGHTBOL,
WellID_BIN, SumWeightBin
FROM
(SELECT WellID, Sand_ID, Sum(weight_DES) as sumWeightDES
FROM T_DESGN) A
INNER JOIN
(SELECT WellID_BOL, Sum(Weight_BOL) as SUMWEIGHTBOL
FROM T_BOL B) B
ON A.Well_ID = B.WellID_BOL
INNER JOIN
(SELECT WellID_BIN, sum(Weight_Bin) as SumWeightBin
FROM T_BIN) C
ON C.Well_ID_BIN = B.Well_ID_BOL
I would simplify it excluding L_WELL and L_SAND. If you are just interestend in IDs, then they really shouldn't be necessary joins. If all the other 3 tables have the WellID and SandID columns, then pick the one that is sure to have all combos.
Supposing it's the Design table, then:
SELECT
WellID_DES AS WellID,
SandID_DES AS SandID,
SUM(Weight_DES) AS Weight_DES,
(SELECT SUM(Weight_BOL) FROM T_BOL WHERE T_BOL.WellID_BOL=d.WellID_DES AND T_BOL.SandID_BOL=d.SandID_DES) AS Weight_BOL,
(SELECT SUM(Weight_BIN) FROM T_BIN WHERE T_BIN.WellID_BIN=d.WellID_DES AND T_BIN.SandID_BIN=d.SandID_DES) AS Weight_BIN
FROM T_DESIGN
GROUP BY WellID, SandID;
... and make sure all your tables have an index on WellID and SandID.
Just to be clear. I dont' think it's a good idea to start the join from the lookup tables, or from their cartesian product. You can always left join them to fetch descriptions and other data. But the main query should be the one with all the combos of WellID and SandID... or if not all, at least the most. Things get difficult if none of the 3 tables (DESIGN, BOL and BIN) have all combos. In that case (and I'd say only in that case) then you might as well start with the cartesian product of the two lookup tables. You could also do a UNION, but I doubt that would be more efficient.
In MySQL Im having two tables:
PRODUCTS (id, Name)
SEEALSO (id, prodLeft, prodRight)
SEEALSO defines which PRODUCTS are related together and are represented as binded fileds "prodLeft"-"prodRight".
For Example:
PRODUCTS:
1 Desk
2 Table
3 Chair
4 Doors
5 Tree
6 Flower
SEEALSO
1 1 2
2 2 3
3 3 4
4 5 6
From that we can see binding of Desk-Table-Chair-Doors and Tree-Flower.
I would now want to write SQL statement where I could specifie PRODUCT name (e.g. Chair) and i would get result of binded fields that are connected with it (e.g. Chair: Desk-Table-Chair-Doors).
From this point on i would like to know if this is even possible for my data presentation concept in SEEALSO and if it is if you could help me solve my problem.
As you're wondering whether it's even possible, you could look into this information on Nested Sets, which is the MySQL way of doing this (I gather).
I could not give you a worked sample, as I'm no MySQL expert: perhaps this will help you enough given the general nature of your question.
For ten years we've been using the same custom sorting on our tables, I'm wondering if there is another solution which involves fewer updates, especially since today we'd like to have a replication/publication date and wouldn't like to have our replication replicate unnecessary entries.I had a look into nested sets, but it doesn't seem to do the job for us.
Base table:
id | a_sort
---+-------
1 10
2 20
3 30
After inserting:
insert into table (a_sort) values(15)
An entry at the second position.
id | a_sort
---+-------
1 10
2 20
3 30
4 15
Ordering the table with:
select * from table order by a_sort
and resorting all the a_sort entries, updating at least id=(2,3,4)
will of course produce the desired output:
id | a_sort
---+-------
1 10
4 20
2 30
3 40
The column names, the column count, datatypes, a possible join, possible triggers or the way the resorting is done is/are irrelevant to the problem.Also we've found some pretty neat ways to do this task fast.
only; how the heck can we reduce the updates in the db to 1 or 2 max.
Seems like an awfully common problem.
The captain obvious in me thougth once "use an a_sort float(53), insert using a fixed value of ordervaluefirstentry+abs(ordervaluefirstentry-ordervaluenextentry)/2".
But this would only allow around 1040 "in between" entries - so never resorting seems a bit problematic ;)
You really didn't describe what you're doing with this data, so forgive me if this is a crazy idea for your situation:
You could make a sort of 'linked list' where instead of a column of values, you have a column for the 'next highest valued' id. This would decrease the number of updates to a maximum of 2.
You can make it doubly linked and also have a column for next lowest, which would bring the maximum number of updates to 3.
See:
http://en.wikipedia.org/wiki/Linked_list
There are similar questions to this, but I don't think anyone has asked this particular question.
Scenario:
Customer - Order (where Order has a CustomerID) - OrderPart - Part
I want a query that returns a customer with all its orders and each order with its parts.
Now I have two main choices:
Use a nested loop (which produces separate queries)
Use data loading options (which produces a single query join)
The question:
Most advice and examples on ORMs suggest using option 2 and I can see why. However, option 2 will potentially be sending back a huge amount of duplicated data, eg:
Option 1 results (3 queries):
ID Name Country
1 Customer1 UK
ID Name
1 Order1
2 Order2
ID Name
1 Part1
2 Part2
3 Part3
Option 2 results (1 query):
ID Name Country ID Name ID Name
1 Customer1 UK 1 Order1 1 Part1
1 Customer1 UK 1 Order1 2 Part2
1 Customer1 UK 1 Order1 3 Part3
1 Customer1 UK 2 Order2 1 Part1
1 Customer1 UK 2 Order2 2 Part2
Option 1 sends back 13 fields with 3 queries. Option 2 sends back 42 fields in 1 query. Now imagine Customer table has 30 fields and Orders have more complex sub joins, the data duplication can quickly become huge.
What impact on overall performance do the following things have:
Overhead of making a database connection
Time taken to send data (potentially across network if on different server)
Bandwidth
Is option 2 always the best choice, option 1 the best choice or does it depend on the situation? If it depends, what criteria should you use to determine? Are any ORMs clever enough to work it out for themselves?
Overhead of making a database connection
Very little if they are on the same subnet, which they usually are. If they're not then this is still not a huge overhead and can be overcome with caching, which most ORMs have (NHibernate has 1st and 2nd level caching).
Time taken to send data (potentially across network if on different server)
For SELECT N+1 this will obviously be longer as it will have to send the select statement each time, which might be up to 1k long. It will also have to grab a new connection from the pool. Chatty versus chunky use to be an argument around 2002-2003 but now it really doesn't make a huge difference unless this is a really big application, in which case you will probably want a more experienced (or better paid) pundit giving his views - i.e. a consultant.
I would favour joins however, as databases will be optimised for this usage over their 10 or more years of development. If performance is really slow a View can sort this out, or Stored Procedure.
By the way, SELECT N+1 is probably the commonest performance problem people experience with NHibernate when they first start using it (including me), and is something that actually takes tweaking to sort out. This is because NHibernate is to ORMs what C++ is to languages.
Bandwidth
An extra SELECT statement for every Customer will eventually build up to however many Customer objects * Orders. So for a large system this might be noticeable - but as I mentioned, ORMs usually have caching mechanisms in place to negate this problem. The amount of SELECT statements also isn't going to be that huge considering:
You're on the same network as the SQL server most of the time
The increased amount of bytes account for about an extra 0.5-50k of extra bandwidth? Think how fast that is on most servers.
a great deal of this is going to depend on the amount of data you are going through.
The join, while returning more fields, is going to run markedly faster (as a rule) than the Option 1 set of queries.
From my personal experience, slow-downs are almost always at that level, the actual running of the query, not the sheer amount of data being passed along whatever pipe you have.