In my application,I have the entity "Department" with Hierarchical structure.
And when I list the department in the page,I want to make them indented as their level in the hierarchical tree,so I add the deep column to identify the location of the current department.
This is the table:
department_id parent_id deep
1 NULL 1
2 1 11
3 1 12
4 2 21
5 3 31
6 2 22
7 6 221
I display them in this manner:
.indent1:{margin-left:5px;}
.indent2:{margin-left:10px;}
.indent3:{margin-left:15px;}
<#list depList as dep>
<span class="indent${dep.deep?length}">${dep.name}</span>
</#list>
Then,each time I insert a new record I have to caculate the value of its deep,I want to know which is the most efficient way?
For example:
If a new Department is created,its paren_id is 2,then the deep if this department to be inserted should be '23',and I want to know how to caculate the value 23,any suggestion?
Update:
It seems that the qustion now is realted to the sql:
I want to select the max length deep field by a given parent.
I can only get the max length deep value in the whole table:
select deep from t_department where length(deep)=(select max(length(deep)) from t_department);
But how about if under a given parent?
Related
This question already has answers here:
What are the options for storing hierarchical data in a relational database?
(7 answers)
Closed 8 months ago.
I am saving data with unknown number of branches in JSON form for now and children can have unknown number of children.
example1 - {employee_1:{employee_2:{employee_3:{}}}}
example2 - {employee_3:{employee_2:employee_1:{}}, employee_4:{employee_3:{}}}
example hierarchical structure
Now to fetch this data, i have to first fetch this hierarchy saved as json and then fetch the id's stored in this json
is there any way to fetch this in one query?
or is there better approach to store and retrieve this?
i am using MySQL
Employee Table
id
name
1
Alice
2
Bob
3
Emily
4
Brian
Example 1 Employee Relation Table
id
parent_id
child_id
1
2
3
2
1
2
Example 2 Employee Relation Table
id
parent_id
child_id
1
4
3
2
2
1
3
3
4
4
3
2
This question already has answers here:
Is storing a delimited list in a database column really that bad?
(10 answers)
Closed 2 years ago.
Hello to Folks out there,
I need some suggestion on How to design MySQL Table Structure for search optimization.
I am creating a Real estate website. In that I have property table and all its associated tables.
I can design my table for saving these records in two ways.
I have amenity master table
id property_name
----------------
1 Property A
2 Property B
3 Property C
Approach 1
Property Table
id property_name
----------------
1 Property A
2 Property B
3 Property C
Property_Amenities table
id p_id amenity_id
------------------------
1 1 1
2 1 2
3 1 3
4 1 4
5 2 1
6 2 1
Approach 2
Property Table
id property_name amenity_id
----------------------------
1 Property A 1,2,3,4,5
2 Property B 1,4,7,9,12
3 Property C 3,4,7,8,9,10
Approach 1 Query : I can join tables and get the all the amenities name for a particular property. Add the required index for optimization. For A property there will be 20 amenities on averages. Suppose I have 100K property records then to get amenities for particular property, MySQL query will search in 2 millions records of Property_Amenities table.
Approach 2 Query : I can search using FIND_IN_SET or IN MySQL operator. But I was going through this search topic and it seems that this approach will be much resource intensive and cost more for same amount of data i.e 100k property records.
Any suggestion will be appropriated. What your thought on this scenario or any other approach I should follow.
Use the first approach. Period. The second is wrong, wrong, wrong. Here are some reasons:
A SQL string should not be used to store multiple values.
Integers should be stored using the proper type.
Foreign key relationships should be declared.
SQL has very poor string handling methods.
SQL has a great way to store lists; it is called a "table" not a "string".
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 have a table which is like a questionnaire type ..
My original table contains 450 columns and 212 rows.
Slno is the person's id who answer the questionaire .
SlNo Q1a Q1b Q2a Q2b Q2c Q2d Q2e Q2f .... Q37c <450 columns>
1 1
2 1 1
3 1
4 1 1
5 1
I have to do analysis for this data , eg Number of persons who is male (Q1a) and who owns a boat (Q2b) i.e ( select * from Questionnaire where Q1a=1 and Q2b=1 ).. etc .. many more combinations are there ..
I have designed in MS access all the design worked perfectly except for a major problem ( Number of table columns is restricted to 255 ).
To be able to enter this into access table i have inserted in as 450 rows and 212 columns (now am able to enter this into access db). Now while fetching the records i want the record set to transpose the results into the form that i wanted so that i do not have to change my algorithm or logic .... How to achieve this with the minimum changes ? This is my first time working with Access Database
You might be able to use a crosstab query to generate what you are expecting. You could also build a transpose function.
Either way, I think you'll stil run into the 255 column limit and MS Access is using temporary table, etc.
However, I think you'll have far less work and better results if you change the structure of your table.
I assume that this like a fill-in-the-bubble questionnaire, and it's mostly multiple choice. In which case instead of recording the result, I would record the answer for the question
SlNo Q1 Q2
1 B
2 B
3 A
4 A C
5 A
Then you have far fewer columns to work with. And you query for where Q1='A' instead of Q1a=1.
The alternative is break the table up into sections (personal, career, etc.) and then do a join, and only show the column you need (so as not to exceed that 255 column limit).
An way to do this that handles more questions is have a table for the person, a table for the question, and a table for the response
Person
SlNo PostalCode
1 90210
2 H0H 0H0
3
Questions
QID, QTitle, QDesc
1 Q1a Gender Male
2 Q1b Gender Female
3 Q2a Boat
4 Q2b Car
Answers
SlNo QID Result
1 2 True
1 3 True
1 4 True
2 1 True
2 3 False
2 4 True
You can then find the question takers by selecting Persons from a list of Answers
select * from Person
where SlNo in (
select SlNo from Answers, Questions
where
questions.qid = answers=qid
and
qtitle = 'Q1a'
and
answers.result='True')
and SlNo in (
select SlNo from Answers, Questions
where
questions.qid = answers=qid
and
qtitle = 'Q2a'
and
answers.result='True')
I finally got the solutions
I created two table one having 225 columns and the other having 225 column
(total 450 columns)
I created a SQL statement
select count(*) from T1,T2 WHERE T1.SlNo=T2.SlNo
and added the conditions what i want
It is coming correct after this ..
The database was entered wrongly by the other staff in the beginning but just to throw away one week of work was not good , so had to stick to this design ... and the deadly is next week .. now it's working :) :)