I have six tables, which unfortunately does not have any primary/foreign key-relations encoded. I've tried to create a view, however I am more than happy with just a table.
I've managed to join the six tables, but after returning 33.5 million rows (cleanInventtrans has 1.7 million rows and every time more tables are added, I am assuming the tables are multiplied by the combination of the previous table) I run out of memory. Now, I realize this is not the correct way of doing this, if it was I'd get a result I am assuming.
I've looked at a couple of questions online
http://www.daniweb.com/web-development/databases/ms-sql/threads/123446/problem-using-join-with-six-tables
SQL joining 6 tables
Unable to relate two MySQL tables (foreign keys)
And I've looked at
http://www.techonthenet.com/sql/joins.php
However, they assume there is a primary-foreign key relationship, my tables do not have this but there are fields which correspond, between the various tables, as seen in the SQL code below. I use these to match up the tables, but somewhere along the line, I am clearly doing it wrong.
I understand that by doing it like this I am essentially multiplying results with each table I join with. I was hoping there was a more clever/correct way of doing it which reduces the amount of results to a management size.
I am unfortunately unable to provide a create statement.
The code I am using:
SELECT dbo.AX_SALESLINE.SALESID, dbo.AX_SALESLINE.ITEMID, dbo.AX_SALESLINE.QTYORDERED, dbo.AX_SALESLINE.SALESPRICE, dbo.AX_SALESLINE.LINEPERCENT,
dbo.AX_SALESLINE.LINEAMOUNT, dbo.AX_SALESLINE.SALESQTY, dbo.AX_SALESLINE.CONFIRMEDDLV, dbo.CleanInventTrans.COSTAMOUNTPOSTED,
dbo.CleanInventTrans.DATEPHYSICAL, dbo.AX_CUSTPACKINGSLIPJOUR.DELIVERYDATE, dbo.AX_SALESTABLE.CUSTACCOUNT, dbo.AX_SALESTABLE.SALESTYPE,
dbo.AX_SALESTABLE.SALESSTATUS, dbo.AX_CUSTPACKINGSLIPJOUR.QTY, dbo.AX_PRODTABLE.PRODID
FROM dbo.AX_CUSTPACKINGSLIPJOUR INNER JOIN
dbo.AX_SALESTABLE INNER JOIN
dbo.CleanInventTrans INNER JOIN
dbo.AX_INVENTTABLE ON dbo.CleanInventTrans.ITEMID = dbo.AX_INVENTTABLE.ITEMID INNER JOIN
dbo.AX_PRODTABLE ON dbo.AX_INVENTTABLE.ITEMID = dbo.AX_PRODTABLE.ITEMID INNER JOIN
dbo.AX_SALESLINE ON dbo.AX_INVENTTABLE.ITEMID = dbo.AX_SALESLINE.ITEMID ON dbo.AX_SALESTABLE.SALESID = dbo.AX_SALESLINE.SALESID ON
dbo.AX_CUSTPACKINGSLIPJOUR.SALESID = dbo.AX_SALESLINE.SALESID
Edit:
Salesline and salestable can be related via P/F-keys, however inventtable and salesline does not have a relationship beyond having a column named itemid, which is the same in both. But these have duplicates and can not function as keys.
Edit2:
Salesline and inventtable cannot be related for some reason:
'AX_INVENTTABLE' table saved successfully
'AX_SALESLINE' table
- Unable to create relationship 'FK_AX_SALESLINE_AX_INVENTTABLE'.
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_AX_SALESLINE_AX_INVENTTABLE". The conflict occurred in database "VS1", table "dbo.AX_INVENTTABLE", column 'ITEMID'.
I've checked the itemid in inventtable, it is unique, and there are multiple of the itemid in the salesline - however not all ID's are numerical in nature, some contain letters. I am not sure if this is what is causing the problem yet.
Edit3:
Foreign-primary relation fails because there are IDs in salines which are not present in the inventtable. Very odd.
Don't bring back all of the rows from these 6 tables. If there are 1million plus rows in some of the tables at least filter on one of these tables, i.e.the CleanIventTrans table using a WHERE clause. If you're not going to add primary and foreign keys, at least add indexes to help improve performance.
Related
SELECT DISTINCT
...
...
...
FROM Reviews Rev
INNER JOIN Reviews SubRev ON Subrev.W_ID=Rev.ID
WHERE Rev.Status='Approved'
This is a small part of a long query that I've been trying to understand for a day now. What is happening with the join? Reviews table appears to be joined with itself, under different aliases. Why is this done? What does it achieve? Also, ID field of the Reviews table is null for the entries that are nevertheless selected and returned. This is correct, but I don't understand how that can happen if the W_ID field is not null.
It allows you to join one row from the table to a different row in the table.
I've both seen this done, and used it myself, in cases where you maybe have a relationship between those rows.
Real-world examples:
An old version of a record and a newer version
Some sort of hierarchical relationship (e.g. if the table contains records of people, you can record that someone is a parent of someone else). There are probably plenty of other possible use cases, too.
SQL allows you to create a foreign key which relates between two different columns in the same table.
Here is my non-updateable query in MS Access 2007:
SELECT [OnlineDirectory].BC_SPEC2
FROM [OnlineDirectory] INNER JOIN Certifs_ABMS
ON [OnlineDirectory].ThisID = Certifs_ABMS.ThisID;
Both OnlineDirectory and Certifs_ABMS:
are local tables with a primary key index.
have indexes ("duplicates okay") on the field ThisID.
The query
has a recordset type of dynaset.
has no record locks.
These are both updateable:
SELECT * FROM [OnlineDirectory]
SELECT * FROM [Certifs_ABMS]
I have reviewed Allen Browne's famous list of hazards and none of them apply. UPDATE: Not true. See accepted answer.
I got excited about adding DISTINCTROW as suggested here, but no success.
How can I make this query updateable?
Both OnlineDirectory and Certifs_ABMS have indexes ("duplicates okay") on the field ThisID.
This is the problem. At least one side of the INNER JOIN needs a unique index (usually a primary key), or the relation is ambiguous.
(Allen Browne: - The fields in a JOIN are not indexed correctly: there is no primary key or unique index on the JOINed fields.)
E.g. if there are in both tables two records each with ThisID = 77. How should the records be matched?
If this is a n:m relation, you need a junction table between them.
I have problem with SQL .
I am trying to create tables from other tables with foreign keys. The table is created normally without problem but when I'm trying to see the data inside the table there is none of the data inside! Anyone who knows?
-- Here is my table with the foreign keys
CREATE TABLE StaffXCustomersXMeals(
--MealID int FOREIGN KEY REFERENCES Meals(MealID),
--CustomersID int FOREIGN KEY REFERENCES Customers(CustomersID),
--StaffID int FOREIGN KEY REFERENCES Staff(StaffID)
)
You might want to consider reading up on the concept of a SQL View - think of it as a "virtual table based on the result-set of an SQL statement." When you create a view based on the JOIN between multiple tables, it saves your query and you can then select from it like you would a table.
For example, you might have the following:
CREATE VIEW StaffCustomerMeals
AS
SELECT
m.MealID,
c.CustomersID,
s.StaffID
FROM
Meals m
LEFT JOIN
Customers c ON
m.SomeIDThatMeansThisCustomer = c.CustomersID
LEFT JOIN
Staff s ON
m.SomeIDThatMeansAStaffMember = s.StaffID
You need to define these relationships in accordance with your own schema - it's your homework assignment, so do your best to figure it out. A couple more questions to consider:
Does a meal always have both a customer and a staff member, or are they customers who might happen to be staff members?
Should you include other information besides the IDs (e.g., CustomerName, StaffMemberDepartment, MealPrice, PurchaseDate)
You didn't enter any data. You only said that whatever data entered must reference the other tables. So you cannot enter invalid meals for instance.
You need INSERT statments to fill the table with whatever data you need.
I need to update one field for a few rows in one table (say, Table_A). However, I'm getting an error message saying conflict with the Foreign Key Constraint in Table_B.
So, I tried to update Table_B as well, turns out Table_B has Foreign Key Constraint with Table_C and Table_D; again, I tried to update Table_C and D, turns out they are conflicting with table_E, F, G, H, I, J, K etc. etc. and on and on.
I was told that such "chain" can go up to 20+ tables.
Additionally, I do not have access to the database schema, thus it is extremely difficult for me to determine which field in which table is the foreign key for the other table.
Currently, all I can do is manually checking each table, all the way from A-Z by using select * statement from the table that is showing in the error message. I'm wondering if there is any alternative to update these specific fields all across tables A till (whichever the last table) directly?
I'm using SQL Server 2005.
This will give you the names of the tables and columns in your foreign keys
SELECT
OBJECT_NAME(fk.[constraint_object_id]) AS [foreign_key_name]
,OBJECT_SCHEMA_NAME(fk.[parent_object_id]) AS [parent_schema_name]
,OBJECT_NAME(fk.[parent_object_id]) AS [parent_table_name]
,pc.[name] AS [parent_column_name]
,OBJECT_SCHEMA_NAME(fk.[parent_object_id]) AS [referenced_schema_name]
,OBJECT_NAME(fk.[referenced_object_id]) AS [referenced_table_name]
,rc.[name] AS [referenced_column_name]
FROM [sys].[foreign_key_columns] fk
INNER JOIN [sys].[columns] pc ON
pc.[object_id] = fk.[parent_object_id] AND
pc.[column_id] = fk.[parent_column_id]
INNER JOIN [sys].[columns] rc ON
rc.[object_id] = fk.[referenced_object_id] AND
rc.[column_id] = fk.[referenced_column_id]
How to best display and analyze the connection graph is a more subjective matter and will depend on the complexity of your schema.
I'm drawing up plans for a few new features on my site, and one could be "solved" using a join table.
Example schema:
Person table
PK PersonId
Name
Age ...
PersonCheckin table
PK FK PersonId
PK FK CheckinId
Date ...
Checkin table
PK CheckinId
CheckedInto ...
A join would be run to get the check in data for a person (connected by the PersonCheckin table). Since every person could check in an unlimited number of times, the PersonCheckin table could become very large.
I'd imagine this would cause some performance issues. What are typical ways this is handled to keep performance high?
A join is considering the best performing means of connecting related tables.
But it really depends on the query, because it might not need to be a JOIN -- JOINing can inflate the record set on the parent tables side if there are more than one child record related, which means there could be a need for either GROUP BY or DISTINCT. EXISTS or IN is a better choice in such situations...
Indexes can help on the column(s) used in the JOIN criteria, on both sides of the relationship. In this example both sides are primary keys, which typically have the best index automatically created when the primary key is defined...
If you are going to execute this query very often and you want to achieve better performance just create a view on the database where you write the join query