SqlLite - SQLite 中带有级联删除的外键？

问题描述 投票：0回答：1

我尝试在子表上使用外键，并在从父表中删除行时收到错误。这是我对Cascade删除的理解。 使用级联删除

具有级联删除功能的外键意味着如果父级中的记录 表被删除，那么子表中对应的记录 会自动删除。这称为级联删除 SQLite。

具有级联删除功能的外键只能在 CREATE 中定义 TABLE 语句。

提示：您不能使用级联删除将外键添加到表中 ALTER TABLE 因为 SQLite 不支持 ADD CONSTRAINT ALTER TABLE 语句。不过，我们稍后会向您展示解决方法 本教程将允许您使用级联添加外键 删除到现有表。

这是我的父表的 DDL。

CREATE TABLE Astro_Target_Imaged (
    ATI_TargetName                TEXT     NOT NULL,
    ATI_Telescope                 TEXT     NOT NULL,
    ATI_FocalLength               TEXT     NOT NULL,
    ATI_SITELONG                  TEXT     NOT NULL,
    ATI_SITELAT                   TEXT     NOT NULL,
    ATI_ICAMERA                   TEXT,
    ATI_ROTNAME                   TEXT,
    ATI_ROTATOR                   TEXT,
    ATI_FWHEEL                    TEXT,
    ATI_FOCNAME                   TEXT,
    ATI_GCAMERA                   TEXT,
    ATI_GSCOPE,
    ATI_Location_Name             TEXT,
    ATI_DataFolder_Location       TEXT,
    ATI_Posted_FinalProcessed_URL TEXT,
    ATI_Bortle                    TEXT (1),
    ATI_Archived                  TEXT (1) DEFAULT N,
    ATI_ArchiveFolderLocation     TEXT,
    ATI_DateAdded                 TEXT,
    ATI_DateLastUpdated           TEXT,
    PRIMARY KEY (
        ATI_TargetName,
        ATI_Telescope,
        ATI_FocalLength,
        ATI_SITELONG,
        ATI_SITELAT
    )
);

这是我应用级联和外键的子表。

CREATE TABLE Astro_Target_Imaged_Date (
    ATI_TargetName          TEXT        NOT NULL
                                        REFERENCES Astro_Target_Imaged (ATI_TargetName) ON DELETE CASCADE,
    ATI_Telescope           TEXT        NOT NULL
                                        REFERENCES Astro_Target_Imaged (ATI_Telescope) ON DELETE CASCADE,
    ATI_FocalLength         TEXT        NOT NULL
                                        REFERENCES Astro_Target_Imaged (ATI_FocalLength) ON DELETE CASCADE,
    ATID_CCYYMMDD           TEXT        NOT NULL,
    ATI_SITELONG            TEXT        NOT NULL
                                        REFERENCES Astro_Target_Imaged (ATI_SITELONG) ON DELETE CASCADE,
    ATI_SITELAT             TEXT        REFERENCES Astro_Target_Imaged (ATI_SITELAT) ON DELETE CASCADE,
    TZ_UTC_Offset           INTEGER (2),
    MI_Illumination_Percent TEXT,
    PRIMARY KEY (
        ATI_TargetName,
        ATI_Telescope,
        ATI_FocalLength,
        ATID_CCYYMMDD,
        ATI_SITELONG,
        ATI_SITELAT
    )
);

错误信息：

[10:45:08] 从表 Astro_Target_Imaged 中删除行时出错： 外键不匹配 - “Astro_Target_Imaged_Date”引用 “Astro_Target_Imaged”

我没有看到名字不匹配，但我可能正在看过去。

sqlite
1个回答
0
投票

根据评论，是的，如果应用，应该可以解决问题。

即外键中指定的父级必须能够引用唯一行（如果存在），而不是潜在的多行。

因此，每个 FKEY 定义必须存在一个 UNQIUE 索引（如果是主键则隐式存在）或通过 UNIQUE 索引显式存在。

在您的情况下，需要 5 个这样的索引，但它们都不存在。然而，您可能想反映父母的独特性。那就是有一个复合的外键定义。

复合外键定义不能在列级别定义，因此必须在表级别定义为约束，语法为：-

https://www.sqlite.org/syntax/table-constraint.html

看来您想要：-

CREATE TABLE IF NOT EXISTS Astro_Target_Imaged_Date (
    ATI_TargetName          TEXT        NOT NULL
                                        -- REFERENCES Astro_Target_Imaged (ATI_TargetName) ON DELETE CASCADE
                                        ,
    ATI_Telescope           TEXT        NOT NULL
                                        -- REFERENCES Astro_Target_Imaged (ATI_Telescope) ON DELETE CASCADE
                                        ,
    ATI_FocalLength         TEXT        NOT NULL
                                        -- REFERENCES Astro_Target_Imaged (ATI_FocalLength) ON DELETE CASCADE
                                        ,
    ATID_CCYYMMDD           TEXT        NOT NULL,
    ATI_SITELONG            TEXT        NOT NULL
                                        -- REFERENCES Astro_Target_Imaged (ATI_SITELONG) ON DELETE CASCADE
                                        ,
    ATI_SITELAT             TEXT        -- REFERENCES Astro_Target_Imaged (ATI_SITELAT) ON DELETE CASCADE
                                        ,
    
    TZ_UTC_Offset           INTEGER (2),
    MI_Illumination_Percent TEXT,
    PRIMARY KEY (
        ATI_TargetName,
        ATI_Telescope,
        ATI_FocalLength,
        ATID_CCYYMMDD,
        ATI_SITELONG,
        ATI_SITELAT
    ),
    FOREIGN KEY (ATI_TargetName,ATI_Telescope,ATI_FocalLength,ATI_SITELONG,ATI_SITELAT)
        REFERENCES Astro_Target_Imaged (ATI_TargetName,ATI_Telescope,ATI_FocalLength,ATI_SITELONG,ATI_SITELAT)
        ON DELETE CASCADE ON UPDATE CASCADE
);
  • note注释掉了原来的列级FKEY定义
  • note 添加了演示更新：-

使用您的代码，按上述修改，然后：-

INSERT INTO Astro_Target_Imaged
    VALUES ('T1','TEL1','F1','SLON1','SLAT200','CAM1','RNAME1','ROR1','W1','FNAME1','GCAM1','GSCOPE1','LOC1','DLOC1','URL1','BORTLE1','ARCY','ARCF1','2024-01-01','2024-01-01')
    ,('T2','TEL1','F1','SLON1','SLAT200','CAM1','RNAME1','ROR1','W1','FNAME1','GCAM1','GSCOPE1','LOC1','DLOC1','URL1','BORTLE1','ARCY','ARCF1','2024-01-01','2024-01-01')
    ,('T3','TEL1','F1','SLON1','SLAT200','CAM1','RNAME1','ROR1','W1','FNAME1','GCAM1','GSCOPE1','LOC1','DLOC1','URL1','BORTLE1','ARCY','ARCF1','2024-01-01','2024-01-01')
    ,('T4','TEL1','F1','SLON1','SLAT200','CAM1','RNAME1','ROR1','W1','FNAME1','GCAM1','GSCOPE1','LOC1','DLOC1','URL1','BORTLE1','ARCY','ARCF1','2024-01-01','2024-01-01')
    ,('T5','TEL2','F1','SLON1','SLAT200','CAM1','RNAME1','ROR1','W1','FNAME1','GCAM1','GSCOPE1','LOC1','DLOC1','URL1','BORTLE1','ARCY','ARCF1','2024-01-01','2024-01-01')
    ,('T6','TEL2','F1','SLON1','SLAT200','CAM1','RNAME1','ROR1','W1','FNAME1','GCAM1','GSCOPE1','LOC1','DLOC1','URL1','BORTLE1','ARCY','ARCF1','2024-01-01','2024-01-01')
    ,('T7','TEL2','F1','SLON1','SLAT200','CAM1','RNAME1','ROR1','W1','FNAME1','GCAM1','GSCOPE1','LOC1','DLOC1','URL1','BORTLE1','ARCY','ARCF1','2024-01-01','2024-01-01')
;
INSERT OR IGNORE INTO Astro_Target_Imaged_Date
    VALUES ('T1','TEL1','F1','2024-01-01','SLON1','SLAT200',10,50)
    ,('T1','TEL1','F1','2024-01-02','SLON1','SLAT200',10,50)
    ,('T1','TEL1','F1','2024-01-03','SLON1','SLAT200',10,50)
    ,('T2','TEL1','F1','2024-01-03','SLON1','SLAT200',10,50)
    ,('T2','TEL1','F1','2024-01-04','SLON1','SLAT200',10,50)
    ,('T3','TEL1','F1','2024-01-01','SLON1','SLAT200',10,50)
    ,('T3','TEL1','F1','2024-01-02','SLON1','SLAT200',10,50)
    ,('T3','TEL1','F1','2024-01-03','SLON1','SLAT200',10,50)
    ,('T5','TEL2','F1','2024-01-01','SLON1','SLAT200',10,50)
    ,('T5','TEL2','F1','2024-01-02','SLON1','SLAT200',10,50)
;
;
SELECT a.ati_targetname, a.ati_telescope,b.atid_ccyymmdd,*  FROM astro_target_imaged AS a JOIN astro_target_imaged_date AS b 
    ON a.ati_targetname = b.ati_targetname
    AND a.ati_telescope = b.ati_telescope
    AND a.ati_focallength = b.ati_focallength
    AND a.ati_sitelong = b.ati_sitelong
    AND a.ati_sitelat = b.ati_sitelat
;
DELETE FROM astro_target_imaged WHERE ati_targetname = 'T1';
SELECT a.ati_targetname, a.ati_telescope,b.atid_ccyymmdd,*  FROM astro_target_imaged AS a JOIN astro_target_imaged_date AS b 
    ON a.ati_targetname = b.ati_targetname
    AND a.ati_telescope = b.ati_telescope
    AND a.ati_focallength = b.ati_focallength
    AND a.ati_sitelong = b.ati_sitelong
    AND a.ati_sitelat = b.ati_sitelat
;
SELECT * FROM astro_target_imaged_date;
UPDATE astro_target_imaged SET ati_targetname = 'UPDATED'||ati_targetname WHERE ati_targetname LIKE '%5';
SELECT a.ati_targetname, a.ati_telescope,b.atid_ccyymmdd,*  FROM astro_target_imaged AS a JOIN astro_target_imaged_date AS b 
    ON a.ati_targetname = b.ati_targetname
    AND a.ati_telescope = b.ati_telescope
    AND a.ati_focallength = b.ati_focallength
    AND a.ati_sitelong = b.ati_sitelong
    AND a.ati_sitelat = b.ati_sitelat
;
SELECT * FROM astro_target_imaged_date;
  • 请注意，前 3 列输出是演示的重要列，因此 
    SELECT a.ati_targetname, a.ati_telescope,b.atid_ccyymmdd,* ....

结果是：-

原来的SELECT:-

  • 插入原始数据的所有排列

从父级删除 T1 后的

SELECT
：-

...._date 表（即级联删除的结果）：-

    即所有 3 个 T1 排列已从被删除的单个 T1 父级中删除

单个T5父级更新后的SELECT：-

和 ...._日期表:-

    即已级联更新
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