I have a table with a column named role and values are as follow:
Scientific staff
PostDocs
Supporting staff
PNUT
Visiting researchers
Secretary
Ph.D. students
Students
Other
I want to use ORDER BY in such a way that Scientific staff comes first. At the moment when I do a query like this, the fields which are Ph.D. students will be returned first (Well because at the moment no row in database has a field with Other in it). Is there a way to achive this using mysql only or should I modify the returned values manually? If so, can you please tell me how?
SELECT * FROM members ORDER BY role
You can do it without an additional table and join, just do:
SELECT * FROM members
ORDER BY
CASE role
WHEN 'Scientific staff' THEN 1
WHEN 'PostDocs' THEN 2
WHEN 'Supporting staff' THEN 5
WHEN 'PNUT' THEN 6
WHEN 'Visiting researchers' THEN 4
WHEN 'Secretary' THEN 3
WHEN 'Ph.D. students' THEN 8
WHEN 'Students' THEN 7
WHEN 'Other' THEN 9
ELSE 10
END
As it is currently implemented, you cannot order by in such a way that Scientific Staff is first, because doing an Oder By sorts it in order of the item in question (in your case, alphabetically it appears by role).
Now, the easy solution to this is to build out a sort priority table with those values in it, assign a numeric priority, then sort by the priority. Let me explain that a little better because it can be confusing:
You make a second table, listing each of these roles, and in a second column give those roles a priority that they will be displayed by.
TABLE:
Role | Priority
Scientific Staff | 1
Ph.D Students | 2
Other | 3
(etc)
You can then do something like this (pseudo-MySQL):
select members.role from members
inner join priority
on members.role = priority.role
order by priority.priority
that will give you the role field from the members table, ordered by the priority you set on the priority table. Since it is an inner join, anyone without a role will not display.
Related
Have two tables users and user_demographics
users has the basic structure of (does have more fields but not needed here):
id name email gender age ethnicity
1 test1 test1#test.com 1 1 1
2 test2 test2#test.com 1 2 1
3 test3 test3#test.com 2 3 2
4 test4 test4#test.com 3 1 1
5 test5 test5#test.com 2 4 5
**Gender**:
1 - Male,
2 - Female,
3 - Prefer not to say
**Age**:
1 - 16-20,
2 - 21-24,
3 - 25-30,
4 - 31-24
**Ethnicity**:
1 - White,
2 - Black,
5 - Prefer not to say
and so on and currently have around 1000 users.
user_demographics structure is:
coreid, type, option (for the sake of this question 'type' will be text, just to make it clearer)
coreid, type option
1 gender 1
1 gender 2
1 age 1
1 age 3
1 ethnicity 1
2 gender 2
2 gender 3
2 age 3
3 gender 1
On a web based form I have 3 sets of checkbox lists, one for each option gender, age, ethnicity and the a user can select multiple from each. They click update and these details are stored in the mysql database as above. coreid is related to another table, but not relevant here.
What I'm trying to do is get a total count of users for each coreid regardless of what type it is. The count should get smaller the more options you select. So coreid 3 should have the biggest count because I've only selected one option.
Example: coreid 3 is selecting all males
Example: coreid 2 is selecting all (females AND 'prefer not to say') AND age range 25-30
Struggling on how to create a single query that will give me the results I need, hope this makes sense.
The idea behind the over all system is that we have a large form that a user fill outs and we store in the information in the users table. Then a member of the admin team can go in and select these users by selecting options from the various demographics information we have collected. So they might just want to see everyone that has ticked the gender options of 'male' and 'prefer not to say' for example. Another admin member may go in and say they want all males, between the age of 25-30. Or they could just tick all options under gender. The idea is that they can select any combination and get a list of results. At the minute I just need to get a count back for the combination selected.
By the SOUNDS of it, you are probably going to need to do with dynamic SQL where you actually build the query on-the-fly, then execute that. Also, to clarify what I THINK you are asking is as follows. CoreID is like a set of filters that some manager is interested in getting count and or details of specific users. They are interested in
EITHER gender condition (1 or 2)
AND EITHER age condition (1 or 3)
AND just the one ethnicity
to possibly target products that might hit those demographics. So you would pre-query every record for CoreID = 1 then start building your query. You would want to order your query by the TYPE to group common items such as the gender, age, ethnicity categories.
Then, within your either localized code (not indicated such as C#, VB, java, whatever), you would need to build the query in such a way that you parenthesis OR those within same category, and logical AND between different such as
where
( Gender = 1
OR Gender = 2 )
AND ( Age = 1
OR Age = 3 )
AND ( Ethnicity = 1 )
If you are trying to write as a MySQL stored procedure, it would be a type of dynamic SQL query... either way, the WHERE clause needs to be constructed from the Core criteria someone is looking for.
You are correct, the last one would be easiest for CoreID = 3 would be a simple
WHERE ( Gender = 1 )
Clarify language source and I or others might be able to offer additional direction, but if I am accurate, you should try to write your own first pass of code, but I will shoot out a pseudo-code for you something like
Get Records Ordered for one CoreID, order by the type of criteria.
prep variable identifying if pending open Parenthesis
prep variable identifying last "type" building for.
for each record
If new type
if has Open Parenthesis
add closing paren
add logical AND before the next entry we are getting
add open parenthesis
set flag we have open parenthesis
else
since same type as last type, add logical OR
go to next record, repeat.
If after last record we would always need to close parenthesis even if a single criteria
I have a Perl program that queries a MySQL database to bring back results based upon which "report" option a user has selected from a web page.
One of the reports is all occupants of a student housing building who have applied for a parking permit, but who have not yet been given one.
When the students apply for a permit, it records the specifics about their car (make, model, year, color, etc.) in a single table row. Each apartment can have up to three students, and each student may apply for a permit. So an apartment might have 0 permits, or 1, 2, or 3 permits, depending upon how many of them have cars.
What I'd like to be able to do, is execute a MySQL query that will find out how many occupants in each apartment have applied for a parking permit, and then based on the results of that query, find out how many permits have been issued. If the number of permits issued is less than the number of applications, that apartment number should be returned in the result set. It doesn't have to name the specific occupant, just the fact that the apartment has at least one occupant who has applied for a permit, but not yet received one.
So I have two tables, one is called occupant_info and it contains all kinds of info about the occupant, but the relevant fields are:
counter (a unique row id)
parking_permit_1_number
parking_permit_2_number
parking_permit_3_number
When a parking permit has been assigned, it is recorded in the appropriate parking_permit_#_number field (if it's occupant number one's permit, it would be recorded in parking_permit_1_number, etc.).
The second table is called, parking_permits, and contains all of the car/owner specifics (make, model, year, owner, owner address, etc.). It also contains a field which references the counter from the occupant_info table.
So an example would be:
occupant_info table
counter | parking_permit_1_number | parking_permit_2_number | parking_permit_3_number
--------|-------------------------|-------------------------|------------------------
1 | 12345 | | 98765
2 | 43920 | |
3 | 30239 | | 34233
parking_permits table
counter | counter_from_occupant_info | permit_1_name | permit_2_name | permit_3_name
--------|----------------------------|---------------|-----------------|-------------------
1 |2 | David Jones | James Cameron | Michael Smerconish
2 |3 | Bill Epps | Hillary Clinton | Donald Trump
3 |1 | Joanne Miller | | Sridevi Gupta
I want a query that will first look at how many occupants in an apartment have applied for a permit. This is determined by counting the names in the parking_permits table. In that table, row 1 has three names, row 2 has three names, and row 3 has two names. The query should then look at the occupant_info table, and for each counter_from_occupant_info from the parking_permits table, see if the same number of parking permits have been issued. This can be determined by comparing the number of non-blank parking_permit_#_number fields.
Using the data above, the query would see the following :
parking_permit table row 1
Has counter_from_occupant_info equal to "2"
Has three names
The row in occupant_info with counter = "2" has only one permit number issued,
so counter_from_occupant_info 2 from parking_permits should be in the result set.
parking_permit table row 2
Has counter_from_occupant_info equal to "3"
Has three names
The row in occupant_info with counter = "3" has only two permit numbers issued,
so counter_from_occupant_info 3 from parking_permits should be in the result set.
parking_permit table row 3
Has counter_from_occupant_info equal to "1"
Has two names
The row in occupant_info with counter = "1" has two permit numbers issued,
so this row should *not* be in the result set.
I've thought about using if, then, case, when, type logic to do this in one query, but frankly can't wrap my head around how to do so.
I was thinking something like:
SELECT
CASE WHEN ( SELECT counter_from_occupant_info
FROM parking_permits
WHERE parking_permit_1_name != ""
AND parking_permit_2_name != ""
AND parking_permit_3_name != "" ) THEN
IF ( SELECT parking_permit_1_number,
parking_permit_2_number,
parking_permit_3_number
FROM occupant_info
WHERE counter = ***somehow reference counter from above case statement--I don't know how to do this***
But then my head explodes and I realize I don't know what the heck I'm doing.
Any help would be appreciated. :-)
Doug
You have a few problems:
Your occupants table schema is bad. There's worse out there, but it looks like someone that doesn't understand how a database works built this table.
Your permits table is also bad. Same reason.
You have no idea what you are doing (kidding... kidding...)
Problem 1:
Your occupants table should probably be two tables. Because an occupant could have 0-3 permits (possibly more, I can't tell from the sample data) then you need a table for your occupant's attributes (name, height, gender, age, primary smell, favorite color, first rent date, I dunno).
Occupants
OccupantID | favorite TV Show | number of limbs | first name | last name | aptBuilding
And... another table for Relationship between the occupant and the permit:
Occupant_permits
OccupantID | Permit ID | status
Now... an occupant can have as many permits as you can stuff into that table and the relationship between them has a status "Applied for", or "Granted" or "Revoked" or what have you.
Problem 2
Your permit info table is doing double duty as well. It holds the information about a permit (it's name) as well as the relationship to the occupant. Since we already have a relationship to the occupant with the "Occupant_Permits" table above, we just need a permits table to hold attributes of a permit:
Permits
Permit ID | Permit Name | Description | etc..
Problem 3
Now that you have a correct schema where objects are in their own table (Occupant, Permit, Occupant and Permit Relationship) your query to get a list of apartments that have at least one occupant that has applied, but not yet received a permit would be:
SELECT
COUNT(DISTINCT o.AptBuilding)
FROM
occupants as o
INNER JOIN occupants_permit as op
ON o.occupant_id = op.occupant_id
INNER JOIN permits as p
ON op.permit_id = p.permit_id
WHERE
op.Status = "Applied"
That's nice and simple and you aren't relying on CASE or UNION or count comparison or any fancy stuff. Just nice straight joins and a simple WHERE clause. This will be fast to query and there's no funny business.
Because your schema isn't great, in order to get something similar you'll need to make use of either UNION queries to stack your many permit_N_ fields into a single field and run something similar to the above query, or you'll have use a fair amount of CASE/IF statements:
SELECT DISTINCT p.pCounter
FROM
(
SELECT
counter as Ocounter
CASE WHEN parking_permit_1_number IS NOT NULL THEN 1 ELSE 0 END
+
CASE WHEN parking_permit_2_number IS NOT NULL THEN 1 ELSE 0 END
+
CASE WHEN parking_permit_3_number IS NOT NULL THEN 1 ELSE 0 END AS permitCount
FROM occupant_info
) as o
LEFT OUTER JOIN
(
SELECT
counter_from_occupant_info as pCounter
CASE WHEN parking_permit_1_name IS NOT NULL THEN 1 ELSE 0 END
+
CASE WHEN parking_permit_2_name IS NOT NULL THEN 1 ELSE 0 END
+
CASE WHEN parking_permit_3_Name IS NOT NULL THEN 1 ELSE 0 END AS permitPermitCount
) as p ON o.Ocounter = p.Pcounter
WHERE p.permitCounter > o.PermitCount
I'm not 100% convinced that is exactly what you are looking for since your schema is confusing where you have multiple objects in a single table and everything is pivoted, but... it should get you in the ball park.
This will be much slower too. There's intermediate result sets, CASE statements, and math, so don't expect MySQL to spit this out in milliseconds.
I have a system with products. Everytime a user enters a product, I insert a record into my database.
I have a table with users and id_products, like this:
users id_product
____________________________
jondoe 2
george 9
jondoe 5
jondoe 2
george 9
george 9
george 2
I need a result (query) wich shows what is TOP visited product id for each user, so the result would be something like this:
jondoes most visited product is ID 2
georges most visitedproduct is ID 9
I was looking for the answer but I am not able to figure it out. Thanks a lot for your help, I appreciate it a lot.
Jan
This is a pain because it involves aggregation. One way to solve this uses a very complicated query. Another uses variables. A third method uses an aggregation trick that works under many circumstances:
select user,
substring_index(group_concat(id_product order by cnt desc), ',', 1) as mostCommonProduct
from (select user, id_product, count(*) as cnt
from t
group by user, id_product
) t
group by user;
One danger when using this method is that the intermediate result might be too long. You can set the group_concat_max_len system variable to get around that particular problem.
i have a query that returns some users related to a specific user (Bob).
I need to retrieve the nearest records, meaning, i must return users whose ID column is near Bob's ID.
For example:
ID
Tom 5
Mike 8
Bob 10
Jack 12
Brian 13
The query:
SELECT users.* FROM users
INNER JOIN neighboors on neighboors.neighboor_id = users.id #ignore this join, just to exemplify
WHERE neighboors.user_id = 10 # bobs id
ORDER BY something
LIMIT 3 # i want to return only the 3 nearest users (according to the table above:mike, jack and brian)
How can i achieve this?
updated
the logic is, users can plant trees, each tree has an specie. The query should return users that have planted the same tree specie.
And why is important order by proximity of id? the client want this way :) there is no other reason.
Try with this, should do what you need :
SELECT users.* FROM users
INNER JOIN neighboors ON neighboors.neighboor_id = users.id
WHERE neighboors.user_id = 10
ORDER BY ABS(neighboors.user_id - 10)
LIMIT 3
The ABS function in this case it is used to calculate the "distance" from user_id selected value (the value filtered by the WHERE ... ).
To obtain better performance on large tables you have to index(if not yet) the column : neighboors.user_id .
One way to do this is to store the differences as a separate column in an inner query and then query for the smallest differences. A good example for nested queries is at :
http://dev.mysql.com/tech-resources/articles/subqueries_part_1.html
The problem is that nearness works in both a positive and negative direction.
If you had:
Tom 5
Mike 8
Sally 9
Bob 10
Sarah 11
Jack 12
Brian 13
Then do you want to return Mike, Sally and Sarah, or Sally, Sarah and Jack? Do you prefer ascending proximity or descending proximity?
It will help to know exactly what business logic this is trying to implement. Why is it important to select by proximity of the ID? How does the ID relate users to each other?
I'd be interested in helping if you can provide more details.
I have a custom shop, and I need to redo the shipping. However, that is sometimes later, and in the meantime, I need to add a shipping option for when a cart only contains a certain range of products.
SO there is a ship_method table
id menuname name zone maxweight
1 UK Standard ukfirst 1 2000
2 UK Economy uksecond 1 750
3 Worldwide Air world_air 4 2000
To this I have added another column prod_restrict which is 0 for the existing ones, and 1 for the restricted ones, and a new table called ship_prod_restrict which contains two columns, ship_method_id and item_id, listing what products are allowed in a shipping category.
So all I need to do is look in my transactions, and for each cart, just check which shipping methods are either prod_restrict of 0 or have 1 and have no products in the cart that aren't in the restriction table.
Unfortunately it seems that because you can't values from an outer query to an inner one, I can't find a neat way of doing it. (edited to show the full query due to comments below)
select ship_method.* from ship_method, ship_prod_restrict where
ship_method.`zone` = 1 and prod_restrict='0' or
(
prod_restrict='1'
and ship_method.id = ship_prod_restrict.ship_method_id
and (
select count(*) from (
select transactions.item from transactions
LEFT JOIN ship_prod_restrict
on ship_prod_restrict.item_id = transactions.item
and ship_prod_restrict.ship_method_id=XXXXX
where transactions.session='shoppingcartsessionid'
and item_id is null
) as non_permitted_items < 1 )
group by ship_method.id
gives you a list of whether the section matches or not, and works as an inner query but I can't get that ship_method_id in there (at XXXXX).
Is there a simple way of doing this, or am I going about it the wrong way? I can't currently change the primary shipping table, as this is already in place for now, but the other bits can change. I could also do it within PHP but you know, that seems like cheating!
Not sure how the count is important, but this might be a bit lighter - hard to tell without a full table schema dump:
SELECT COUNT(t.item) FROM transactions t
INNER JOIN ship_prod_restrict r
ON r.item_id = t.item
WHERE t.session = 'foo'
AND r.ship_method_id IN (**restricted, id's, here**)