I have a table of money owed, along with a team identifier (could be 1,2,3 for example)
I have another table which gives a name to these team identifiers (so 1 could refer to Team1, 2 could refer to John's jokers etc)
The first table can have multiple entries for money owed and I need to get the total owed per team identifier, and use the team name if it exists.
So I left join the tables and use a sum clause and get a total amount owed per teamname, or null if the teamname is not present. If it is null then I want to use the team identifier, so the results would look like
name total
.....................
team1 100
John's jokers 1000
99 50
where 99 is a team identifier because there was no teamname and there was a null present.
I tried using ifnull(columnName, teamID) but this failed when using a sum clause.
Could anyone help with this problem please
I think ifnull() is used like this:
select ifnull(teams.team_name, teams.team_id) from teams;
So in this case it tries to retrieve the name of the team, and if that comes back null it instead uses the team's identifier. In this case your query would look like this:
select ifnull(teams.team_name, owing.team_id), sum(amount_owed)
from owing left join teams on owing.team_id = teams.id
group by owing.team_id
Make sure the group by asks for the ID field from owing, not teams, otherwise you'll be grouping on a null field.
Does this resolve the issue?
Related
I have a table like so:
Customer Purchase Date Product
Frank 7/28/2015 Hammer
Bob 7/29/2015 Shovel
Bob 7/29/2015 Pickaxe
Bill 7/30/2015 Pliers
The Purchase Date field records a new entry for every purchase. So, if in one visit a customer purchases four items, my database creates four entries each with the same date.
I'm trying to write a query that displays the numbers of visits for each customer. Output like so:
Frank 1
Bob 1
Bill 1
But when I use the COUNT function on the date in my query, it returns:
Frank 1
Bob 2
Bill 1
I want my query to only count unique dates, but the COUNT function doesn't work. Everywhere I read, it also says that the SQL COUNT (Distinct) doesn't work in Access. Access help says that if I set the Query Properties to Unique Values "Yes", it should only return unique values, but it doesn't work. I tried Unique Record "Yes" also, but that didn't work either.
Please help! Thanks!
Try this:
select Cust, count(cust) as CustomerCount
from (Select Distinct Table1.Customer as cust, Table1.PurchaseDate
from Table1)
group by cust
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.
I have two tables.
Table Emp
id name
1 Ajay
2 Amol
3 Sanjay
4 Vijay
Table Sports
Sport_name Played by
Cricket ^2^,^3^,^4^
Football ^1^,^3^
Vollyball ^4^,^1^
Now I want to write a query which will give me output like
name No_of_sports_played
Ajay 2
Amol 1
Sanjay 2
Vijay 2
So what will be Mysql query for this?
I agree with the above answers/comments that you are not using a database for what a database is for, but here is how you could calculate your table from your current structure in case you have no control over that:
SELECT Emp.name, IF(Played_by IS NULL,0,COUNT(*)) as Num_Sports
FROM Emp
LEFT JOIN Sports
ON Sports.Played_by RLIKE CONCAT('[[:<:]]',Emp.id,'[[:>:]]')
GROUP BY Emp.name;
See it in action here.
UPDATE: added the IF(Played_by IS NULL,0,COUNT(*)) instead of COUNT(*). This means that if an employee doesn't play anything they'll have a 0 as their Num_Sports. See it here (I also added in those ^ characters and it still works.
What it does is joins the Emp table to the Sports table if it can find the Emp.id in the corresponding Played_by column.
For example, if we wanted to see what sports Ajay played (id=1), we could do:
SELECT *
FROM Emp, Sports
WHERE Sports.Played_by LIKE '%1%'
AND Emp.id=1;
The query I gave as my solution is basically the query above, with a GROUP BY Emp.name to perform it for each employee.
The one modification is the use of RLIKE instead of LIKE.
I use RLIKE '[[:<:]]employeeid[[:>:]]' instead of LIKE '%employeeid%. The [[:<:]] symbols just mean "make sure the employeeid you match is a whole word".
This prevents (e.g.) Emp.id 1 matching the 1 in the Played_by of 3,4,11,2.
You do not want to store your relationships in a column like that. Create this table:
CREATE TABLE player_sports (player_id INTEGER NOT NULL, sport_id INTEGER NOT NULL, PRIMARY KEY(player_id, sport_id));
This assumes you have an id column in your sports table. So now a player will have one record in player_sports for each sport they play.
Your final query will be:
SELECT p.name, COUNT(ps.player_id)
FROM players p, player_sports ps
WHERE ps.player_id = p.id
GROUP BY p.name;
Evening folks,
I have a complex MySQL COUNT query I am trying to perform and am looking for the best way to do it.
In our system, we have References. Each Reference can have many (or no) Income Sources, each of which can be validated or not (status). We have a Reference table and an Income table - each row in the Income table points back to Reference with reference_id
On our 'Awaiting' page (the screen that shows each Income that is yet to be validated), we show it grouped by Reference. So you may, for example, see Mr John Smith has 3 Income Sources.
We want it to show something like "2 of 3 Validated" beside each row
My problem is writing the query that figures this out!
What I have been trying to do is this, using a combination of PHP and MySQL to bridge the gap where SQL (or my knowledge) falls short:
First, select a COUNT of the number of incomes associated with each reference:
SELECT `reference_id`, COUNT(status) AS status_count
FROM (`income`)
WHERE `income`.`status` = 0
GROUP BY `reference_id`
Next, having used PHP to generate a WHERE IN clause, proceed to COUNT the number of confirmed references from these:
SELECT `reference_id`, COUNT(status) AS status_count
FROM (`income`)
WHERE `reference_id` IN ('8469', '78969', '126613', ..... etc
AND status = 1
GROUP BY `reference_id`
However this doesn't work. It returns 0 rows.
Any way to achieve what I'm after?
Thanks!
In MySQL, you can SUM() on a boolean expression to get a count of the rows where that expression is true. You can do this because MySQL treats true as the integer 1 and false as the integer 0.
SELECT `reference_id`,
SUM(`status` = 1) AS `validated_count`,
COUNT(*) AS `total_count`
FROM `income`
GROUP BY `reference_id`
While very easy to do in Perl or PHP, I cannot figure how to use mysql only to extract the first unique occurence of a record.
For example, given the following table:
Name Date Time Sale
John 2010-09-12 10:22:22 500
Bill 2010-08-12 09:22:37 2000
John 2010-09-13 10:22:22 500
Sue 2010-09-01 09:07:21 1000
Bill 2010-07-25 11:23:23 2000
Sue 2010-06-24 13:23:45 1000
I would like to extract the first record for each individual in asc time order.
After sorting the table is ascending time order, I need to extract the first unique record by name.
So the output would be :
Name Date Time Sale
John 2010-09-12 10:22:22 500
Bill 2010-07-25 11:23:23 2000
Sue 2010-06-24 13:23:45 1000
Is this doable in an easy fashion with mySQL?
I think that something along the lines of
select name, date, time, sale from mytable order by date, time group by name;
will get you what you're looking for
you need to perform a groupwise max or groupwise min
see below or http://pastie.org/973117 for an example
select
u.user_id,
u.username,
latest.comment_id
from
users u
left outer join
(
select
max(comment_id) as comment_id,
user_id
from
user_comment
group by
user_id
) latest on u.user_id = latest.user_id;
In databases, there really is no "first" or "last" record; think of each record as its own, non-positional entity in the table. The only positions they have are when you give them one, say, using ORDER BY.
This will give you what you want. It might not be efficient, but it works.
select Name, Date, Time, Sale from
(select Name, Date, Time, Sale from MyTable
order by Date asc, Time asc) MyTable_subquery_name
group by Name
Note: MyTable_subquery_name is just a dummy name for the subquery. MySQL will give the error ERROR 1248 (42000): Every derived table must have its own alias without it.
If only GROUP BY and ORDER BY were communicative operations, then this wouldn't have to be a subquery.