I have a table that contains information about an item, and another table that references the owner of that item, like so:
baseItem
--------
itemID | 1 | 2 | 3 | 4 |
itemSize | 5 | 1 | 5 | 3 |
itemCost | 100 | 50 | 1 | 99 |
itemOwner
--------
ownerID | 1 | 1 | 3
itemID | 1 | 4 | 2
What I'm after are the SUMS of itemSize and itemCOST based on the owner. I've looked around but none of the answers I've seen make sense? Here's the best I could come up with, which clearly isn't working:
SUM itemCost FROM baseItem.itemCost LEFT JOIN itemID ON itemOwner.itemid = baseItem.itemid
SELECT ownerId, sum(itemCost) as OwnerCost, sum(itemSize) as OwnerSize
FROM itemOwner
LEFT JOIN baseItem
ON itemOwner.itemid = baseItem.itemid
GROUP BY ownerId
A SELECT statement lists which fields you want to read from the table; in this case you want two values: the id of the owner, and the sum of the values of the items they own. However, since you're using sum (an aggregate function), you must GROUP your elements over some parameter. In this case, you want to group them by ownerId.
A FROM clause references a table; you can start with either baseItem or itemOwner, it makes no difference in this case. You can think of LEFT JOIN as a cartesian product that creates a new table, which contains every element from the cartesian product of both, filtered by the ON clause. However will always have all the items in the left table which is itemOwner and when there are no matching rows in the baseItem all the fields will be NULL. The SUM function will act as if those are 0s and should return you a 0 sum for non matching rows in the baseItem table.
Maybe it is not working because it is invalid SQL statement. Try following code
SELECT SUM(baseItem.itemCost) FROM baseItem
LEFT JOIN itemOwner ON itemOwner.itemId = baseItem.itemId
Related
I have the following tables:
Users
id | name
-----------------
1 | Johny Bravo
Orders
id | users_id | number
----------------------
1 | 1 | 111111
2 | 1 | 222222
3 | 1 | 333333
4 | 1 | 444444
Example
id | text | number
------------------
1 | test | 111111
2 | test | 111111
3 | test | 222222
4 | test | 222222
5 | test | 333333
6 | test | 333333
Desired Outcome
id: 1
name: Johny Brawo
count(orders): 4
count(example): 6
My current query, which doesn't work
SELECT users.id, users.name, count(orders.id), count(example.id)
FROM users
LEFT JOIN orders ON orders.users_id=users.id
LEFT JOIN example ON example.number=orders.number
GROUP BY users.id
My current result
id: 1
name: Johny Brawo
count(orders): 8
count(example): 8
Any help would be greatly appreciated.
try count(distinct orders.id), count(distinct example.id)
I've not done any MySQL really, but this works in other Databases...
Starting - a little bit of theory. What does your query do?
First it SELECTs something from users table.
Then it LEFT JOINs with orders table. Number of returned rows is a multiplication of rows from users table and matching rows from orders table. So with only this join you will have 6 rows, each one with Johny Bravo as user, but with different orders data.
Then - another LEFT JOIN. This time with example table. Again - a number of returned rows is a multiplication of rows from orders table and matching rows from example table. So without GROUP BY and COUNT you will have eight rows of result.
Now, the GROUP BY query part. What does it do? It just groups rows with matching GROUP BY column(s). So it will group all rows with same users.id. There are eight of them.
Standard COUNT() will return a number of rows with not null value. As there were eight rows, both counts will return 8.
Now, as #GPW suggested, the solution is a COUNT(DISTINCT x). This function returns a count of unique not null rows.
Thus, the query should look like:
SELECT users.id, users.name, count(DISTINCT orders.id), count(DISTINCT example.id)
FROM users
LEFT JOIN orders ON orders.users_id=users.id
LEFT JOIN example ON example.number=orders.number
GROUP BY users.id
UPDATE - ordering and strict databases
You have also asked about ordering the result. You can order it by any column from your query. As MySQL is not very strict when it comes to grouping, you will also be able to order by any column from users table, as users table results are unique (grouped by id). You can also add, for example ORDER BY COUNT(DISTINCT orders.id) DESC to find users with largest number of orders.
Most databases, though, is more strict in GROUP BY queries. It allows to SELECT only columns with aggregated values or those explicitly contained in GROUP BY clause. So your GROUP BY clause should rather look like
GROUP BY users.id, users.name
I found this query that can combine two tables with different number of rows and without any related fields:
SELECT a.*, b.* FROM table1 a, table2 b;
Now my problem is that in my case I cannot change the value of the FROM.
Example I have this Query:
SELECT * FROM table1;
I cannot change that to:
SELECT * FROM table2;
At most, I can only add statements after FROM table_name LEFT JOIN somedefaulttable ON somedefaulttable2.id = somedefaulttable .id_c. (I forgot to add this important detail, I can only add custom queries after this line, I cannot remove this predetermined LEFT JOIN as this is system generated) The reason for this is because I am restricted by the CRM I am using, and I cannot edit the default select value but I can add additional custom queries after the said statement.
Now what my main problem here is that I need to combine a different table in my Query and I cannot use join as they don't have any common values and their number of rows are also different, I also tried using JOIN before to no avail, and thus decided to try using a different approach such as merging the two tables.
This is the link to my previous question where I was using JOIN to achieve my goal of combining the tables. In this link, you can see that I want to combine Table A and Table 4 but I cannot do so with JOIN as they have a different number of rows and that I am limited in changing my current Query to fit the posted answer.
Table A.
id | name | deleted | amount | due_date | status
1 | a | 0 | 10 | 2016-07-18 | Unpaid
2 | b | 0 | 20 | 2016-07-19 | Unpaid
3 | c | 0 | 15 | 2016-07-18 | Unpaid
Table B
id | name | due_date | status
1 | a | | Unpaid
2 | b | | Unpaid
3 | c | | Unpaid
4 | d | 2016-07-19 | Unpaid
Table C
id | table_d_id | table_a_id
1 | 1 | 1
2 | 2 | 2
3 | 3 | 3
Table D
id |
1
2
3
Try this for (inner) joining two tables without a JOIN Statement.
SELECT a.x, a.y, b.x, b.y FROM table1 a, table2 b WHERE a.x = b.x
What I do not understand is, how different numbers of rows affect the requested solution.
i have created a link of one to many between the tables
with your example and number of rows you inserted you should try this:
SELECT TableC.*
FROM TableB, TableD INNER JOIN (TableA INNER JOIN TableC ON TableA.ID = TableC.table_a_id) ON TableD.ID = TableC.table_d_id;
this will bring all the records of table C
I have a table with all my invoice items as packages:
Table: invoice_items
invoice_item_id | package_id | addon_1 | addon_2 | addon_3 | ...
----------------|------------|---------|---------|
1 | 6 | 2 | 5 | 3 |
Then my other table:
Table: addons
addon_id | addon_name | addon_desc |
----------|--------------|--------------------------|
1 | Dance Lights | Brighten up the party... |
2 | Fog Machine | Add some fog for an e... |
Instead of taking up space storing the addon name in my invoice_items table, I'd like to just include the addon_id in the addon_1, addon_2, etc columns.
How do I then get the name of the addon when doing a query for invoice_item rows?
Right now I just have it programmed into the page that if addon_id == 1, echo "Dance Lights", etc but I'd like to do it in the query. Here is my current query:
$invoice_items_SQL = "
SELECT invoice_items.*, packages.*
FROM `invoice_items`
INNER JOIN packages ON invoice_items.invoice_item_id = packages.package_id
WHERE `event_id` = \"$event_id\"
";
So I'm able to do this with packages, but only because there's just one package_id per row, but there are up to 9 addons :(
The most direct way of doing it is to join onto the table multiple times. That's a bit naff though because you'll write almost the same thing 9 times.
Another, better way would be to restructure your tables - you need another table with 2 data columns: invoice_id and addon_id. You then need either an auto-inc primary column, or use both of those existing columns as a dual primary key. So this is a many-to-many junction table.
From there you can can query without having 9 repetitive joins, but you will get a row of each package for every addon it has (so if it has three addons it will appear three times in the results). And then from there you can use GROUP_CONCAT to concatenate the names of the addons into a single field so that you only get one row per invoice.
take the case you have 2 table, for example tbCostumers and tbOrders.
I would like to display a summary list with all costumers, related orders and display them with a paginator.
Doing a join I can extract costumers list and all orders for each costumer, the result is something like:
idCostumer | name | ... | idProduct | productName | price | ...
Where the first n columns are all equal if the costumer has more than 1 order. So I can have:
1 | will | ... | 12 | product1 | 123 | ...
2 | bill | ... | 23 | product2 | 321 | ...
2 | bill | ... | 24 | product3 | 231 | ...
And so on
I'm trying to use LIMIT to extract only n records and using them with a paginator.
First question: if a costumer has more than 1 order, with this query I'll see n records, equal in the first column (id, name, ... and other costumer info) but different at the end, where there are products info. Is this 'correct'? Is there another way to extract this informations?
Second question: if I do that and I use a LIMIT, I could "cut" the result table between 2 (or more) records that represent the same customer; so, for example in the small table above, if I limit with 2 the third row will be lost, even if it's part of the row above, because is just another order of the same costumer.
I would like to limit the number of different idCostumer, in order to take exactly n costumers, even if they appear more than 1 times in the result table. Something like n different idCostumer, no matter if they are repeated.
Is this possible?
I hope it's clear, it was not easy to explain what I would like to achieve :)
Thank you!
You might want to have something like this:
SELECT * FROM (
(SELECT * FROM tbCustomers LIMIT 3) AS c
INNER JOIN tbOrders AS o ON o.customer = c.idcustomer
);
You can substitute the first asterisk with named columns and only receive your desired columns in the order you prefer (ie: SELECT c.name, o.price FROM...) .
Hope this works for you!
EDIT: changing the value of the LIMIT clause changes the number of the picked customers, of course.
EDIT 2: As Alvaro Pointed out, you'll probably need an order clause in the tbCustomers query.
I am trying to migrate some custom CMS DB to Wordpress, and so far it's been a living hell.
I am using WP All import plugin, so I need a neat single .csv export that contains data from multiple tables from this custom cms database.
So, these are the columns from two tables that I want to join:
`eo_items`
| cat_id | identificator | create_date |
---------------------------------------------
| 1 | Title of the post | 1283786285 |
`eo_items_trans`
| item_id | lid | name | s_desc | l_desc |
---------------------------------------------------------
| 1 | 33 | Title of the post | excerpt | content |
Desired result should be:
| item_id | lid | name | s_desc | l_desc | cat_id | create_date |
--------------------------------------------------------------------------------
| 1 | 33 | Title of the post | excerpt | content | 1 | Some date |
Here is the script I am using:
SELECT DISTINCT
eo_items_trans.item_id,
eo_items_trans.lid,
eo_items.cat_id,
DATE_FORMAT( eo_items.create_date, '%d.%m.%Y' ) create_date,
eo_items_trans.s_desc,
eo_items_trans.l_desc,
eo_items_trans.name
FROM eo_items_trans
LEFT JOIN eo_items ON ( eo_items_trans.name = eo_items.identificator )
Trouble with this code is that in resulting table some date columns are NULL, and I don't know if the result is what I need because the table has around 2000 rows and I don't know how to cross check if category IDs are correctly populated.
This is the first time I am doing something like this with MySQL so I am really not sure if the procedure is right for what I am trying to achieve.
If you need any clarifications please ask.
EDIT:
eo_items table has some 300 rows more than eo_items_trans so there are some records there that don't have corresponding records in eo_items_trans. I am guessing this should be reflected in the query as well?
Since you're using a LEFT JOIN, NULLs will be returned for any rows of eo_items_trans that do not have entries in oe_items. This could mean the eo_items.identificator is empty, or doesn't exactly match the name (case sensitivity will apply).
You'll have to investigate and clean up the data for rows in eo_items_trans missing the expected row in eo_items.
You NULL results for date seem to come or from eo_items_trans records that have no corresponding entry in the eo_items table or from eo_items records where create_date is null.
You can easily crosscheck check by doing the following
Is there records in eo_items_trans that have no corresponding entries in eo_items:
SELECT DISTINCT eo_items_trans.name FROM eo_items_trans
where NOT EXISTS (
SELECT * FROM eo_items
where eo_items.identificator = eo_items_trans.name
)
If this yields one ore more rows, that will be the eo_items_trans.name records with no correspondent in eo_items. If this is you problem, the do a JOIN, not a LEFT join in your main query
As for empty dates in eo_items you might want to check like this
SELECT * from eo_items WHERE create_date IS NULL
If you find records here, this is where yout NULL values in the main query come from