I've done some research and I know about building views but I feel like what I am trying to accomplish may not be possible without creating a hard coded table of information..Below is what I am trying to accomplish
Table 1
ID
1
2
3
4
5
Table 2
ID DATE
1 4/23/2014
1 5/10/2014
2 4/15/2014
5 12/13/2013
3 3/15/2014
What I am wanting to do is compose a query that will start with the data in table one as it contains all possible ID's, I want to join this data with the data from table 2 based on the ID field, but the key is I will be passing in a date argument that will be filtering the data based on month and year as well. What I need to happen is if an ID in table one does not have a record in Table 2 for a given month I need a null record to be created. The issue I am running into is not having a single null record no matter what for each ID in table one being put into the view which below I explain why I need this. Here is the view I am getting with just typical left join:
Table 3 (View or just a general query joining the above tables)
ID DATE
1 4/23/2014
1 5/10/2014
2 4/15/2014
5 12/13/2013
3 3/15/2014
4 null
Now its easy to see if I pulled for this data for the month/year of 4/2014 or null I would get
ID DATE
1 4/23/2014
2 4/15/2014
4 null
What I am looking to get (which I realize is impossible from the data in this view) is:
ID DATE
1 4/23/2014
2 4/15/2014
4 null
3 null
5 null
So is there a way to create these rows in a view dynamically so that when I pass in my date argument I will get the desired results? One thing I just thought of right this second would be to create a view with just the ID's from table 1 and a null date field and possibly union the two views together? Or could a Union be used in building the initial view to get the desired results? Once I have the data in the final view (or pulling it with the correct query in general) I will be able to accomplish my final task of building reports based on the data. Any help would be greatly appreciated!
Related
Environment: MySQL 5.6
SqlTable name = CategoryTable
Sql Columns
CATEGORY_ID (INT)
CATEGORY_NAME (VARCHAR)
LEVEL (INT)
MOTHER_CATEGORY (INT)
I've tried with
SELECT
CATEGORY_ID, CATEGORY_NAME , LEVEL , MOTHER_CATEGORY
FROM
CategoryTable
But I don't know how to use the ORDER BY in order to get that result.
So the first line here are the columns, and from the second lines, there start the table content:
CATEGORY_ID CATEGORY_NAME LEVEL MOTHER_CATEGORY
1 MainCategory 0 0
2 -SubCategory1 1 1
3 --SubCategory2 2 2
4 ---SubCategory3 3 3
5 2Nd_Main_Category 0 0
6 -SubCategory1 1 5
7 --SubCategory2 2 6
8 ---SubCategory3 3 7
is there a way to achieve something like this with a mysql query?
You aren't very clear in what you are trying to achieve. I'll take a guess that you want to order using a multi-level parent child structure. there are some very complicated ways of handling such a feat within mysql 5.6, a DB that's not really ideal for such a structure, but I have come up with something simple myself that I use in my own apps. you create a special ordering field that creates a path of zero filled ids for each record.
ordering_path_field
/
/0000000001/
/
/0000000001/0000000002
/0000000003
/0000000003/0000000005
/0000000003/0000000005/0000000006
etc
so each record contains a path of each parent up to the root, using zero filled ids. then you can just sort by this field to get them in proper order. the drawbacks being that you'll have to set a max number of levels allowed, so that the ordering fields doesn't overflow, and also, moving a record to a new parent if ever needed would be a big pain.
Transport table
id name
1 T1
2 T2
Pallets table
id name
1 P1
2 P2
Transport Pallet Capacity table
id transport_id pallet_id capacity
1 1 1 10
2 1 2 null
3 2 1 20
4 2 2 24
How to generate table like this:
id transport_id pallet_id_1_capacity pallet_id_2_capacity
1 1 10 null
2 2 20 24
Problem: pallets and transports can be added, so, neither quantity is known in advance.
For example, manager adds another pallet type and 'pallet_id_3_capacity' column should be generated (and can show null if no capacity data is yet available).
Another manager can fill 'transport pallet capacity' table later when notified.
Is there a way to build sql in mysql that will care about the above: specifically - dynamic number of pallets?
The SQL select-list must be fixed at the time you write the query. You can't make SQL that auto-expands its columns based on the data it finds.
But your request is common, it's called a pivot-table or a crosstab table.
The only solution is to do this in multiple steps:
Query to discover the distinct pallet ids.
Use application code to build a dynamic SQL query with as many columns as distinct pallet id values found in the first query.
Run the resulting dynamic SQL query.
This is true for all SQL databases, not just MySQL.
See MySQL pivot row into dynamic number of columns for a highly-voted solution for producing a pivot-table query in MySQL.
I am not voting your question as a duplicate of that question, because your query also involves transport_id, which will make the query solution a bit different. But reading about other pivot-table solutions should get you started.
SELECT column_1 FROM table_1,table_2;
When I ran this on my database it returned huge number of rows with duplicate column_1 values. I could not understand why I got these results. Please explain what this query does.
it gives you a cross product from table 1 and table 2
In more layman's terms, it means that for each record in Table A, you get every record from Table B (all possible combinations).
TableA with 3 records and Table B with 3 records gives 9 total records in the result:
TableA-1/B-1
TableA-1/B-2
TableA-1/B-3
TableA-2/B-1
TableA-2/B-2
TableA-2/B-3
TableA-3/B-1
TableA-3/B-2
TableA-3/B-3
Often used as a basis for Cartesian Queries (which themselves are the means to generate, say, a list of future dates based on a recurrence schedule: give me all possible results for the next 6 months, then restrict that set to those whose factor matches my day of the week)
This is 'valid' way of cross joining two tables; it is not the preferred way though. Cross Join would be much clearer. An on condition would then be helpful to limit results,
Imagine that i have 3 friends named Jhon, Ana, Nick; then i have in the other table 2 are T-shirts a red and a yellow and i wanna know witch is from.
So in the query being tableA:Friends and tableB:Tshirts returns:
1|JHON | t-shirt_YELLOW
2|JHON | t-shirt_RED
3|ANA | t-shirt_YELLOW
4|ANA | t-shirt_RED
5|NICK | t-shirt_YELLOW
6|NICK | t-shirt_RED
As you see this join has no relational logic between friends and Tshirts so by evaluating all the posible combination generates what you call duplicates.
I have a table (t1) in mySQL that generates the following table:
type time full
0 11 yes
1 22 yes
0 11 no
3 13 no
I would like to create a second table (t2) from this that will summarize the information found in t1 like the following:
type time num_full total
0 11 1 2
1 22 1 1
3 13 0 1
I want to be able to iterate through the type column in order to be able to start this summary, something like a for-loop. The types can be up to a value of n, so I would rather not write n+1 WHERE statements, then have to update the code every time more types are added.
Notice how t2 skipped the type of value 2? This has also been escaping me when I try looping. I only want the the types found to have rows created in t2.
While a direct answer would be nice, it would be much more helpful to be pointed to some sources where I could figure this out, or both.
This may do what you want
create table t2 if not exists select type, time, sum(full) num_full, count(*) count
from t1
group by type,time
order by type,time;
depending on how you want to aggregate the time column.
This is a starting point for reference on the group by functions : https://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html
here for create syntax
https://dev.mysql.com/doc/refman/5.6/en/create-table.html
I need to create a join query for hierarchical data across 2 tables. These tables can have unlimited amounts of data and their structures are as follows:
group_id group_name group_order
1 group 1 2
2 group 2 1
field_id field_name parent_group field_order
1 field 1 1 1
2 field 2 2 2
3 field 3 2 1
I am currently able to get the correct format of data using 2 select queries with the second query inside a loop created from the results of the first query on the groups table.
The structure of the data I require from the result is as follows:
-group 2
- field 3
- field 2
- group 1
- field 1
Is it possible to get these results from one mysql query? I have read through the mysql document on hierarchical data by I am confused about how to incorporate the join.
Thanks for looking
You shouldn't need to think about it in terms of hierarchical data, you should just be able to select your fields and join on your group information. Try something like:
SELECT *
FROM Fields AS F
INNER JOIN Groups AS G
ON G.group_id = F.parent_group
ORDER BY group_order, field_order
Then you will get each fields as a row with the applicable group, also in the correct group order. Your loop should be able to handle the display you need.
one method
something that may convince you change your db schema