mysql的创建表上删除集空

Question

我想创建与删除/更新约束的多个外键数据库多个外键，但我得到一个错误代码1005的以下SQL脚本：

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; 

错误代码表示无法创建Vineyard表，我只想知道用删除/更新控件创建多个外键的正确格式。

Answer 1

您的外键规则是ON DELETE SET NULL，但您的列定义是NOT NULL。

要么更改您的列定义，并删除NOT NULL部分或者过度使用您的外键规则。这一工程：

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

Answer 2

访问：

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; 

Answer 3

尝试用无外键创建表（innoDB enginer），并使用update table with constraint语法，用于例如：

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; 

参考：

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

绝招：不建议在表的名称中使用大写字母（或骆驼）该行为与操作系统不同克用于：

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

Answer 4

访问：

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 
    );