Mysql create table with multiple foreign key on de

问题:

I am trying to create a database with multiple foreign keys with delete/ update constraints, but I got a error code 1005 with following sql scripts:

CREATE TABLE Worker (
 WorkerID smallint auto_increment,
 WorkerType  varchar(45) NOT NULL,
 WorkerName  varchar(45) NOT NULL,
 Position    varchar(45) NOT NULL,
 TaxFileNumber int NOT NULL,
 Address    varchar(100) ,
 Phone      varchar(20) ,
 SupervisorID  smallint ,
 PRIMARY KEY (WorkerID),
 FOREIGN KEY (SupervisorID) REFERENCES Worker(WorkerID)
    ON DELETE SET NULL
    ON UPDATE CASCADE
)Engine=InnoDB;

CREATE TABLE Grape (
    GrapeID smallint NOT NULL,
    GrapeType varchar(45) NOT NULL,
    JuiceConversionRatio int,
    StorageContainer ENUM('Stainless Steel Tank','Oak Barrel'),
    AgingRequirement int,
    PRIMARY KEY (GrapeID)
)Engine=InnoDB;

CREATE TABLE Vineyard (
    VineyardID smallint auto_increment,
    VineyardName VARCHAR(45) NOT NULL,
    FarmerID    smallint NOT NULL,
    GrapeID smallint NOT NULL,
    ComeFrom    varchar(45) NOT NULL,
    HarvestedAmount int,
    RipenessPercent int,
    PRIMARY KEY (VineyardID),
    FOREIGN KEY (FarmerID) REFERENCES Worker(WorkerID)
        ON DELETE SET NULL
        ON UPDATE CASCADE,
    FOREIGN KEY (GrapeID) REFERENCES Grape(GrapeID)
        ON DELETE SET NULL
        ON UPDATE CASCADE
)Engine=InnoDB;

The error code says that fail to create the Vineyard table, I just want to know the proper format for creating multiple foreign keys with delete/update control.

回答1:

Your foreign key rule is ON DELETE SET NULL but your column definition is NOT NULL.

Either change your column definition and remove the NOT NULL part or overthink your foreign key rule. That works:

CREATE TABLE Vineyard (
    VineyardID smallint auto_increment,
    VineyardName VARCHAR(45) NOT NULL,
    FarmerID    smallint,
    GrapeID smallint,
    ComeFrom    varchar(45) NOT NULL,
    HarvestedAmount int,
    RipenessPercent int,
    PRIMARY KEY (VineyardID),
    FOREIGN KEY (FarmerID) REFERENCES Worker(WorkerID)
        ON DELETE SET NULL
        ON UPDATE CASCADE,
    FOREIGN KEY (GrapeID) REFERENCES Grape(GrapeID)
        ON DELETE SET NULL
        ON UPDATE CASCADE
)Engine=InnoDB;

SQLFiddle demo

回答2:

Try with create table(innoDB enginer) without foreign key and use the update table with constraint syntax, for example:

ALTER TABLE `vineyard`
        ADD CONSTRAINT `relation_farmer_has_many_vineyards`
            FOREIGN KEY (`farmer_id`)
            REFERENCES `worker` (`worker_id`)
            ON DELETE SET NULL
            ON UPDATE CASCADE;

Reference:

• http://dev.mysql.com/doc/refman/5.6/en/innodb-foreign-key-constraints.html

Trick: is not recommended to use capital letters(or camel case) in the names of the tables that the behavior differs from the operating system being used:

• http://dev.mysql.com/doc/refman/5.1/en/identifier-case-sensitivity.html

回答3:

Visit :

https://developer.android.com/training/basics/data-storage/databases.html#DefineContract

Cursor c = db.query(
    FeedEntry.TABLE_NAME,                     // The table to query
    projection,                               // The columns to return
    selection,                                // The columns for the WHERE clause
    selectionArgs,                            // The values for the WHERE clause
    null,                                     // don't group the rows
    null,                                     // don't filter by row groups
    sortOrder                                 // The sort order
    );

回答4:

Visit :

http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html

CREATE TABLE `ffxi_characterJob` (
`serverID` int(11) NOT NULL,
`userid` int(10)unsigned NOT NULL,
`characterName` varchar(255) NOT NULL,
`jobAbbr` char(4) NOT NULL,
`jobLevel` int(11) default '0',
PRIMARY KEY (`serverID`,`userid`,`characterName`,`jobAbbr`),
INDEX (`jobAbbr`),
CONSTRAINT FOREIGN KEY (`serverID`,`userid`,`characterName`) REFERENCES `ffxi_characters` (`serverID`,`userid`,`characterName`) 
ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT FOREIGN KEY (`jobAbbr`) REFERENCES `ffxi_jobType` (`jobAbbr`) ON DELETE CASCADE ON UPDATE CASCADE
) TYPE=InnoDB;