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mysqlsqljoinleft-joincross-join

unknown column in on clause error

Hey guys I am this close in being able to represent the data that I wish to display The column in question is a.state_Id. I understand from the research I have done that the a.State_Id is out of scope. What is the missing piece to my sql statement?

If I take out the a.State_ID = c.State_Id leaving only the b.Product_Id = c.Product_Id then the data is displayed but I need to match against the state and product.

I know i need to add in another join somewhere but im not sure how. If anyone could help me that would be awesome!

SELECT a.state_id, 
       a.state_name, 
       a.state_abbreviatedname, 
       b.product_id, 
       b.product_name, 
       c.stateproduct_price 
FROM   states a, 
       products b 
       LEFT OUTER JOIN stateproducts c 
ON a.state_id = c.state_id AND b.product_id = c.product_id

Update 1

The states table has been populated and contains the following fields:

State_Id
State_Name
State_AbbreviatedName

The Products table which has been populated to contain the base products. This table has the following fields:

Product_Id
Product_Name

Each state will have the same products however the price for each product changes with each state. This is why i have the StateProducts table. This table is empty and will be populated one by one by an interface I have created. The statesproducts table will have the following fields

State_Id //reference/relational field to be user for comparison
Product_Id //reference/relational field to be user for comparison
StateProduct_Price //new field

so i understand that i will receive NULL values in the price column.

I have been able to return a sort of cartesion product of the States and products table. However I now need to append the price for each combination on the right side of this cartesion table. bearing in mind that stateproducts table is empty how would i accomplish this?

Solution

  • I guess you have a Many-to-Many relationship in which States can have multiple Products and Products can be on different States. So you need to join States into the mapping table StateProducts so you can be able to get the products on table Products.

    SELECT  a.State_ID, 
        a.State_Name, 
        a.State_AbbreviatedName, 
        b.Product_Id, 
        b.Product_Name, 
        c.StateProduct_Price
FROM    States a
        INNER JOIN StateProducts c
            ON a.State_ID = c.State_Id
        INNER  JOIN Products b 
            ON b.Product_Id = c.Product_Id

    To further gain more knowledge about joins, kindly visit the link below:

    UPDATE 1

    use CROSS JOIN keyword,

    SELECT a.state_id, a.state_name, a.state_abbreviatedname, b.product_id, b.product_name, c.stateproduct_price 
FROM   states a 
       CROSS JOIN products b 
       LEFT OUTER JOIN stateproducts c
          ON a.state_id = c.state_id AND 
             b.product_id = c.product_id