wall_paths (table)
wall_dimensions
dimensions (reference table)
What I've got so far:
Query
SELECT wall_paths.wall_id, wall_paths.wall_path,
dimensions.width, dimensions.height
FROM wall_paths
LEFT JOIN wall_dimensions
ON wall_paths.wall_id = wall_dimensions.wall_id
LEFT JOIN dimensions
ON wall_dimensions.dimension_id = dimensions.dimension_id
WHERE wall_paths.wall_id = 4;
Result
The query is selecting redundant rows, I just would like to select the two paths along with the corresponding dimensions based on the wall_dimensions table. Something like below:
Expected result
Result with GROUP BY in query
Please help on how to select something like the above.
Note: I've tried DISTINCT as well on the query but returns an error.
The query results are as expected, actually. Makes sense when you see it, data-wise. The data model is setup incorrectly for this query.
Fiddle (original data model): http://sqlfiddle.com/#!2/8c1bf/1
Fiddle (modified data model): http://sqlfiddle.com/#!2/3d9b0/5
Not saying you should change your model, just pointing out the query runs as expected with the current schema.
Related
I just can't see the problem with how I'm making my foreign keys and I'm just really confused why I keep getting the wrong result. Here are screenshots from my workbench
Here are my tables:
And here's my diagram
I've also tried to normalize my tables and I was kinda expecting my query to return a similar result like in the sample table (Questions table) where it will only show 2 results since I want to query where idsurvey = 1 I made in this image:
My question is that, how do I fix my foreign key so that if I want to query
select * from survey.survey, survey.questions where idsurvey = 1
it will only return 2 rows? (based on sample data in the workbench screenshot)
Any comments and suggestions on my diagram would also be greatly appreciated.
When you have two tables in the from clause, every row from the first table is matched with every table from the second table. This is known as a Cartesian Product. Usually, this isn't the behavior you'd want (like it isn't in this case), and you'd use a condition to tell the database how to match these two tables:
SELECT *
FROM survey.survey s, survey.questions q
WHERE s.idsurvey = q.survey_id AND idsurvey = 1
While this should work, it's quite outdated to use multiple tables in the same from clause. You should probably use an explicit join clause instead:
SELECT *
FROM survey.survey s
JOIN survey.questions q ON s.idsurvey = q.survey_id
WHERE idsurvey = 1
I have these two tables:
Achievement:
Achieves:
Question:
I want to retrieve rows from table Achievement. But, I do not want all the rows, I want the rows that a specific Steam ID has acquired. Let's take STEAM_0:0:46481449 for example, I want to check first the list of IDs that STEAM_0:0:46481449 has acquired (4th column in Achieves table states whether achievement is acquired or not) and then read only those achievements.
I hope that made sense, if not let me know so I can explain a little better.
I know how to do this with two MySQL statements, but can this be done with a single MySQL statement? That would be awesome if so please tell me :D
EDIT: I will add the two queries below
SELECT * FROM Achieves WHERE Achieves.SteamID = 'STEAM_0:0:46481449' AND Achieves.Acquired = 1;
Then after that I do the following query
SELECT * FROM Achievement;
And then through PHP I would check the IDs that I should take and output those. That's why I wanted to get the same result in 1 query since it's more readable and easier.
In sql left join, applying conditions on second table will filter the result when join conditions doesn't matter:
Select * from achievement
left join achieves on (achievement.id=achieves.id)
where achieves.acquired=1 and achieves.SteamID = 'STEAM_0:0:46481449'
Besides,I suggest not using ID in the achieves table as the shared key between two tables. Name it something else.
I don't think a left join makes sense here. There is no case where you don't want to see the Achievement table.
Something like this
SELECT *
FROM Achieves A
JOIN Achievement B on A.ID = B.ID
WHERE A.SteamID = 'STEAM_0:0:46481449'
AND A.Acquired = 1;
I have this 2 two views. I made a view out of them because they have dependencies on other tables. I then created a query joining them together. Two queries separately has over 30k plus data.
Sample Query would be like:
Select main.*, detail.*
FROM main_data as main
INNER JOIN detail_data AS details ON (main.id = detail.main_id)
WHERE main.column_data LIKE '%something%'
This is slow but if I comment out the "detail.*" on the column section with the join being there is returns the data very fast. What is wrong here?
The expected amount of data is only 20 rows. Still takes very long to perform the select. What makes it slow?
I'd like to add that the joined tables on the view are correct. It is joined accordingly. Like I said If queried separately it returns a lot of data in a very short time.
For more details, actually there is a third table here where both table are a child to. I changed it up to something like this. It improves the performance a bit.
Select main.*, detail.*
FROM parent_data AS par
INNER JOIN main_data as main ON (par.id = detail.par_id)
INNER JOIN detail_data AS details ON (par.id = detail.par_id)
WHERE main.column_data LIKE '%something%'
I made a EXPLAIN SELECT on the exact tables and this is there result:
Thank you.
The only reason the query slows down if you include fields in the resultset from detail table is that detail.main_id is indexed, therefore if no fields are selected from detail, then mysql does not have to touch detail table, it is enough to use the index only. If you do include some fields from that table, then simple index lookup will not be enough, mysql will have to open detail table and get the corresponding records from there.
Try using left join cause you need only connected records from right table:
Select main.*, detail.*
FROM main_data as main
LEFT JOIN detail_data AS details
ON (main.id = detail.main_id AND main.column_data LIKE '%something%')
Good day,
I am trying to join 3 tables for my inventory report but I am getting weird results out of it.
my query
SELECT i_inventory.xid,
count(x_transaction_details.xitem) AS occurrence,
i_inventory.xitem AS itemName,
SUM(i_items_group.or_qty) AS `openingQty`,
avg(x_transaction_details.cost) AS avg_cost,
SUM(x_transaction_details.qty) AS totalNumberSold,
SUM(i_items_group.or_qty) - SUM(x_transaction_details.qty) AS totalRemQty
FROM x_transaction_details
LEFT JOIN i_inventory ON x_transaction_details.xitem = i_inventory.xid
LEFT JOIN i_items_group ON i_inventory.xid = i_items_group.xitem
WHERE (x_transaction_details.date_at BETWEEN '2015-01-18 03:14:54' AND '2015-10-18 03:14:54')
AND i_inventory.xid = 3840
GROUP BY x_transaction_details.xitem
ORDER BY occurrence DESC
This query gives me this result:
See the openingQty column, I then tried to do a simple query to verify the result,
here's my query for checking the openingQty with joining only 2 tables i_items_group table (batches are stored) and i_inventory table (item Information are stored).
SELECT i_inventory.xid,
i_inventory.xitem,
SUM(i_items_group.or_qty) AS openingQty,
i_items_group.cost
FROM i_inventory
INNER JOIN i_items_group ON i_inventory.xid = i_items_group.xitem
WHERE i_inventory.xid = 3840
AND (i_items_group.date_at BETWEEN '2015-01-18 03:14:54' AND '2015-10-18 03:14:54')
my result was:
which is the correct data.
I also made a query on my x_transaction_details table also to verify if its correct or not.
heres my query:
select xitem, qty as qtySold from x_transaction_details where xitem = 3840
AND (date_at BETWEEN '2015-01-18 03:14:54' AND '2015-10-18 03:14:54')
result:
Which would total to: 15-quatitySold.
I'm just confused on how did I get 3269 as a result of my query where as the true openingQty should be only 467.
I guess the problem was in my query with joins, its messing up with number of transactions then it sums it up (I really dont know though).
Can you please help me identify it, and help me come up with the correct query.
This is a common problem with multiple SUM statements in a single query. Keep in mind how SQL does aggregation: first it generates a set of data that is not aggregated, then it aggregates it. Try your query without the GROUP BY or aggregate functions, and you'll be surprised what you turn up. There aren't enough of the right details in your post for me to determine where the breakdown is, but I can guess.
It looks like you have an xitem corresponding to some kind of product, then you have joined that to both transactions and items groups. Suppose a particular xitem matches with 3 transactions and 5 item groups. You'll get 15 records from that join. And when you sum it, any SUM calculations based on fields from the transaction table will be 5x higher than you expect, and any SUM calculations from the item groups table will be 3x higher than you expect. The key symptom here is the aggregate result being a multiple of the correct value, but seemingly different multiples for different rows.
There are multiple ways to address this kind of error. Some developers like to calculate one of hte aggregates in a subquery, then do the other aggregate in the main query and group by the already correct result from the subquery. Others like to write in-line queries to do the aggregate right in the expression:
SELECT xitem, (SELECT SUM(i_items_group.or_qty) FROM i_items_group WHERE i_inventory.xid = i_items_group.xitem) AS `openingQty`
, -- select more fields
Find what approach works best for you. But if you want to see the evidence for yourself, run this query with the aggregates gone and you'll see why those SUMs are doing what they are doing:
SELECT i_inventory.xid,
x_transaction_details.xitem AS occurrence,
i_inventory.xitem AS itemName,
i_items_group.or_qty,
x_transaction_details.cost,
x_transaction_details.qty,
i_items_group.or_qty - x_transaction_details.qty AS RemainingQty
FROM x_transaction_details
LEFT JOIN i_inventory ON x_transaction_details.xitem = i_inventory.xid
LEFT JOIN i_items_group ON i_inventory.xid = i_items_group.xitem
WHERE (x_transaction_details.date_at BETWEEN '2015-01-18 03:14:54' AND '2015-10-18 03:14:54')
AND i_inventory.xid = 3840
ORDER BY occurrence DESC
I'm having an issue getting this SQL query to work properly.
I have the following query
SELECT apps.*,
SUM(IF(adtracking.appId = apps.id AND adtracking.id = transactions.adTrackingId, transactions.payoutAmount, 0)) AS 'revenue',
SUM(IF(adtracking.appId = apps.id AND adtracking.type = 'impression', 1, 0)) AS 'impressions'
FROM apps, adtracking, transactions
WHERE apps.userId = '$userId'
GROUP BY apps.id
Everything is working, HOWEVER for the 'impressions' column I am generating in the query, I am getting a WAY larger number than there should be. For example, one matching app for this query should only have 72 for 'Impressions' yet it is coming up with a value of over 3,000 when there aren't even that many rows in the adtracking table. Why is this? What is wrong here?
Your problem is you have no join conditions, so you are getting every row of every table being joined in your query result - called a cartesian product.
To fix, change your FROM clause to this:
FROM apps a
LEFT JOIN adtracking ad ON ad.appId = a.id
LEFT JOIN transactions t ON t.adTrackingId = ad.id
You haven't provided the schema for your tables, so I guessed the names of the relevant columns - you may have to adjust them. Also, your transaction table may join to adtracking - it's impossible to know from your question, so agin you have have to alter things slightly. Hopefully you get the idea.
Edit:
Note: your group-by clause is incorrect. You either need to list every column of apps (not recommended), or change your select to only select the id column from apps (recommended). Change your select to this:
SELECT apps.id,
-- rest of query the same
Otherwise you'll get weird, incorrect, results.