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Multiple Foreign Keys?

- 1 answer

I've got a table that is supposed to track days and costs for shipping product from one vendor to another. We (brilliantly :p) stored both the shipping vendors (FedEx, UPS) with the product handling vendors (Think... Dunder Mifflin) in a "VENDOR" table. So, I have three columns in my SHIPPING_DETAILS table that all reference VENDOR.no. For some reason MySQL isn't letting me define all three as foreign keys. Any ideas?

CREATE TABLE SHIPPING_GRID(  
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY COMMENT 'Unique ID for each row',  
    shipping_vendor_no INT(6) NOT NULL COMMENT 'Foreign key to VENDOR.no for the shipping vendor (vendors_type must be 3)',  
    start_vendor_no INT(6) NOT NULL COMMENT 'Foreign key to VENDOR.no for the vendor being shipped from',  
    end_vendor_no INT(6) NOT NULL COMMENT 'Foreign key to the VENDOR.no for the vendor being shipped to',  
    shipment_duration INT(1) DEFAULT 1 COMMENT 'Duration in whole days shipment will take',  
    price FLOAT(5,5) NOT NULL COMMENT 'Price in US dollars per shipment lbs (down to 5 decimal places)',  
    is_flat_rate TINYINT(1) DEFAULT 0 COMMENT '1 if is flat rate regardless of weight, 0 if price is by lbs',  
    INDEX (shipping_vendor_no),  
    INDEX (start_vendor_no),  
    INDEX (end_vendor_no),  
    FOREIGN KEY (shipping_vendor_no) REFERENCES VENDOR (no),  
    FOREIGN KEY (start_vendor_no) REFERENCES VENDOR (no),  
    FOREIGN KEY (end_vendor_no) REFERENCES VENDOR (no)  
) TYPE = INNODB;

Edited to remove double primary key definition...


Yeah, unfortunately that didn't fix it though. Now I'm getting:

Can't create table './REMOVED MY DB NAME/SHIPPING_GRID.frm' (errno: 150)

Doing a phpinfo() tells me this for mysql:

Client API version 5.0.45

Yes, the VENDOR.no is type int(6).

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Answer

You defined the primary key twice. Try:

CREATE TABLE SHIPPING_GRID(  
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY COMMENT 'Unique ID for each row',  
    shipping_vendor_no INT(6) NOT NULL COMMENT 'Foreign key to VENDOR.no for the shipping vendor (vendors_type must be 3)',  
    start_vendor_no INT(6) NOT NULL COMMENT 'Foreign key to VENDOR.no for the vendor being shipped from',  
    end_vendor_no INT(6) NOT NULL COMMENT 'Foreign key to the VENDOR.no for the vendor being shipped to',  
    shipment_duration INT(1) DEFAULT 1 COMMENT 'Duration in whole days shipment will take',  
    price FLOAT(5,5) NOT NULL COMMENT 'Price in US dollars per shipment lbs (down to 5 decimal places)',  
    is_flat_rate TINYINT(1) DEFAULT 0 COMMENT '1 if is flat rate regardless of weight, 0 if price is by lbs',  
    INDEX (shipping_vendor_no),  
    INDEX (start_vendor_no),  
    INDEX (end_vendor_no),  
    FOREIGN KEY (shipping_vendor_no) REFERENCES VENDOR (no),  
    FOREIGN KEY (start_vendor_no) REFERENCES VENDOR (no),  
    FOREIGN KEY (end_vendor_no) REFERENCES VENDOR (no)  
) TYPE = INNODB;

The VENDOR primary key must be INT(6), and both tables must be of type InnoDB.

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source: stackoverflow.com
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