Hi (sorry for the poor title),
I have two tables in a MySQL DB, lets call them CarMake and CarModel. Both tables have two fields, ID:int(11) and Description:varchar(100). For example:
CarMake CarModel
ID Description | ID Description
-----------------------------------------------------
123456 Honda | 12345678 Accord
234567 Toyota | 12345665 Civic
369258 Lexus | 23456789 Prius
Where each car model shares the same first 6 digits of the ID of its Make. In this example, both Accord and Civic share the first 6 digits of the ID with Honda, therefore they are Honda models.
Now, what I want to do is select all rows from CarMake that do not have a record in CarModel where the first 6 digits of the ID match. In this example, my query should return the Lexus row from CarMake, as it does not have a matching row in CarModel.
Nothing I have tried so far has really come close to achieving what I want, so I am posting it here.
Any help would be greatly appreciated!
EDIT: Solved with help from zerkms
SELECT * FROM CarMake
LEFT JOIN CarModel
ON CarModel.ID LIKE CONCAT(CarMake.ID, '%')
WHERE CarModel.ID IS NULL;
Follow up questions:
This solution takes a very long time to run, is there any way to improve efficiency?
What would be the best way to delete the records returned by that query? Is there some way I can combine that into the query itself?
Related
Here's my situation : I have a table that has large amounts of records, I need to pull out a number of these records for each name in the database, note that TOP will not work for my use case. My end user wants the report formatted in such a way that each user shows up only once, and up to 3 different dates are shown for the user.
Table format
AutoID
Enum
TNum
Date
Comments
1
25
18
2/2/22
2
25
18
1/2/21
Blah
3
18
18
1/2/21
4
18
18
1/2/20
5
25
17
1/2/22
6
25
17
1/2/20
Now the Enum and TNum fields are fk with other tables, I have created a join that pulls the correct information from the other tables. In the end my query provides this output
RecordID
Training
CompletedDate
FirstName
LastName
Location
2821
MaP
1/1/21
David
Simpson
123 Sesame St.
2822
1/2/22
Fuller
MaP
Dough
GHI
David
123 Sesame St.
2825
1/1/20
Simpson
The two "Blank fields" represent information that is pulled and may or may not be needed in some future report.
So to my question : How do I manage to get a report, with this query's pull to look like this:
Place
LastName
FirstName
Training
FirstCuttoff
Secondcutoff
ThirdCutoff
Comments
123 Sesame St.
David
Simpson
MaP
1/1/20
1/1/21
123 Sesame St.
John
Dough
MaP
1/1/22
I was originally planning on joining my query to itself using where clauses. But when I tried that it just added two extra columns of the same date. In addition it is possible that each record is not identical; locations may be different but since the report needs the most recent location and the name of the trainee. In addition, to add more complexity, there are a number of people in the company with effectively the same name as far as the database is concerned, so rejoining on the name is out. I did pull the Enum in my query, I can join on that if needed.
Is there an easier way to do this, or do I need to sort out a multiple self-joining query?
I have a project I am working on where I am going to have to do this. Some of the suggestions I received were to use a Pivot query. It wouldn't work in my case but it might for yours. Here is a good example
Pivot Columns
I'm just learning PHP and MySQL and I have two tables in the same database : FirstYear , SecondYear that have a structure like this :
StudentId |Math | Physics StudentId1 | Math1 | physics1
Joe 10 14 Alan 12 17
Alan 13 17 Smith 11 13
Smith 9 9 Joe 10 15
Is it possible to write a query that select and compare the two columns StudentId , StudentId1 to find matched records and if for example Joe=Joe after that compare records of math with math1 and physics with physics1 that are in the same row as matched records of StudentId with StudentId1 ;the idea of this query is to study the improvement of same student from first year to the second one ,Thanks .
Yes, it is possible but you have to complete SQL fundamental course.
In this situation you have to know about JOIN. Such as, Inner Join, Left Join, Right Join, Full Join etc. Also, compare with unique id, not name. Because, name always duplicate. It is not good practice. So, Know about primary key and foreign key.
However,
Query-
SELECT * FROM FirstYear INNER JOIN SecondYear ON FirstYear.StudentId = SecondYear.StudentId1 WHERE FirstYear.id = 1
Something like that, alternatively, you can try to another logic.
I am wondering if any of you would be able to help me. I am trying to loop through table 1 (which has duplicate values of the plant codes) and based on the unique plant codes, create a new record for the two other tables. For each unique Plant code I want to create a new row in the other two tables and regarding the non unique PtypeID I link any one of the PTypeID's for all inserts it doesnt matter which I choose and for the rest of the fields like name etc. I would like to set those myself, I am just stuck on the logic of how to insert based on looping through a certain table and adding to another. So here is the data:
Table 1
PlantCode PlantID PTypeID
MEX 1 10
USA 2 11
USA 2 12
AUS 3 13
CHL 4 14
Table 2
PTypeID PtypeName PRID
123 Supplier 1
23 General 2
45 Customer 3
90 Broker 4
90 Broker 5
Table 3
PCreatedDate PRID PRName
2005-03-21 14:44:27.157 1 Classification
2005-03-29 00:00:00.000 2 Follow Up
2005-04-13 09:27:17.720 3 Step 1
2005-04-13 10:31:37.680 4 Step 2
2005-04-13 10:32:17.663 5 General Process
Any help at all would be greatly appreciated
I'm unclear on what relationship there is between Table 1 and either of the other two, so this is going to be a bit general.
First, there are two options and both require a select statement to get the unique values of PlantCode out of table1, along with one of the PTypeId's associated with it, so let's do that:
select PlantCode, min(PTypeId)
from table1
group by PlantCode;
This gets the lowest valued PTypeId associated with the PlantCode. You could use max(PTypeId) instead which gets the highest value if you wanted: for 'USA' min will give you 11 and max will give you 12.
Having selected that data you can either write some code (C#, C++, java, whatever) to read through the results row by row and insert new data into table2 and table3. I'm not going to show that, but I'll show how the do it using pure SQL.
insert into table2 (PTypeId, PTypeName, PRID)
select PTypeId, 'YourChoiceOfName', 24 -- set PRID to 24 for all
from
(
select PlantCode, min(PTypeId) as PTypeId
from table1
group by PlantCode
) x;
and follow that with a similar insert.... select... for table3.
Hope that helps.
My question about SEARCH query performance.
I've flattened out data into a read-only Person table (MySQL) that exists purely for search. The table has about 20 columns of data (mostly limited text values, dates and booleans and a few columns containing unlimited text).
Person
=============================================================
id First Last DOB etc (20+ columns)...
1 John Doe 05/02/1969
2 Sara Jones 04/02/1982
3 Dave Moore 10/11/1984
Another two tables support the relationship between Person and Activity.
Activity
===================================
id activity
1 hiking
2 skiing
3 snowboarding
4 bird watching
5 etc...
PersonActivity
===================================
id PersonId ActivityId
1 2 1
2 2 3
3 2 10
4 2 16
5 2 34
6 2 37
7 2 38
8 etc…
Search considerations:
Person table has potentially 200-300k+ rows
Each person potentially has 50+ activities
Search may include Activity filter (e.g., select persons with one and/or more activities)
Returned results are displayed with person details and activities as bulleted list
If the Person table is used only for search, I'm wondering if I should add the activities as comma separated values to the Person table instead of joining to the Activity and PersonActivity tables:
Person
===========================================================================
id First Last DOB Activity
2 Sara Jones 04/02/1982 hiking, snowboarding, golf, etc.
Given the search considerations above, would this help or hurt search performance?
Thanks for the input.
Horrible idea. You will lose the ability to use indexes in querying. Do not under any circumstances store data in a comma delimited list if you ever want to search on that column. Realtional database are designed to have good performance with tables joined together. Your database is relatively small and should have no performance issues at all if you index properly.
You may still want to display the results in a comma delimted fashion. I think MYSQL has a function called GROUP_CONCAT for that.
I am trying to store a family tree.
Here is the platform that I am using, Zend framework, Mysql, Ajax
I have searched stackoverflow I came across this post which is very helpful in handling data in terms of objects.
"Family Tree" Data Structure
I'll Illustrate my use case in brief.
User can create family members or friends based on few relations defined in database. I have Model for relations too. User can create family members like Divorced spouse, frineds. Max the Tree can be deep that we are assuming max to kids of the grandchildren but it can expand in width too. Brother/sister & their family.
I am looking an efficient database design for lesser query time. If I have to use the data structures described in above post where I must keep them as they necessary have to be a Model.
For representation I am planning to use Visualization: Organizational Chart from
http://code.google.com/apis/chart/interactive/docs/gallery/orgchart.html#Example
I'll summarize what I need
Database design
Placing of controllers (ajax) & models
The people that the user will create they will not be any other users. just some another data
yeah thats it! I'll post a complete solution on this thread when I'll be completing the project, of course with help of expertise of u guys
Thanks in advance
EDIT I I'll Contribute more to elaborate my situation
I have a user table, a relation table, & last family/family tree table
the Family table must have similar structure to following
ID userid relation id Name
1 34 3 // for son ABC
2 34 4 // for Wife XYZ
3 34 3 // for Mom PQR
4 34 3 // for DAd THE
5 34 3 // for Daughter GHI
6 34 3 // for Brother KLM
The drawback for this approach is generating relations to the other nodes like daughter-in-law, wifes brother & their family.
The ideal way of doing is for a user we can add Parents, siblings, children & for extra relations they must be derived from the family members relation i.e. Brother-in-law must be derived as sister's husband, or wife's brother.
THis is what I can think now. I just need Implementation guidelines.
Hope this helps u guys to provide a better solution.
I guess that from the database point of view it would be best to implement it like
id | name | parent_male | parent_female
Other option would be string prefixing
id | name | prefix
1 | Joe | 0001
2 | Jack | 000100001 //ie. Joes son
3 | Marry| 0001 //ie. Jacks mother
4 | Eve | 0002 // new family tree
5 | Adam | 00020001 // ie. Eves son
6 | Mark | 000200010001 // ie. Adams son
Other (more effective) algorithms like MPTT assume that the data is a tree, which in this case is not (it has circles).
To show it would work - to select Mark's grandparents:
--Mark
SELECT prefix FROM family_tree WHERE id = 6;
-- create substring - trim N 4-character groups from the end where N is N-th parent generation => 2 for grandparent ==> 0002
--grandparents
SELECT * FROM family_tree WHERE prefix = '0002'
-- same for other side of family
-- cousins from one side of family
SELECT * FROM family_tree WHERE prefix LIKE '0002%' AND LENGTH(prefix) = 12