1

我基本上创建了一些表来玩：我有两个主表和一个多对多连接表。这是 DDL：（我正在使用 HSQLDB）

CREATE TABLE PERSON
(
    PERSON_ID INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY, 
    NAME VARCHAR(50), MAIN_PERSON_ID INTEGER
)

CREATE TABLE JOB
(
    JOB_ID INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY, 
    NAME VARCHAR(50)
)
CREATE TABLE JOB_PERSON
(
    PERSON_ID INTEGER, 
    JOB_ID INTEGER
)
ALTER TABLE JOB_PERSON ADD 
    CONSTRAINT FK_PERSON_JOB FOREIGN KEY(PERSON_ID) 
    REFERENCES PERSON ON DELETE CASCADE ON UPDATE CASCADE 

ALTER TABLE JOB_PERSON ADD
    CONSTRAINT FK_JOB_PERSON FOREIGN KEY(JOB_ID) 
    REFERENCES JOB ON DELETE CASCADE ON UPDATE CASCADE

ALTER TABLE PERSON ADD
    CONSTRAINT FK_PERSON_PERSON FOREIGN KEY(MAIN_PERSON_ID) 
    REFERENCES PERSON ON DELETE CASCADE ON UPDATE CASCADE

insert into person values(null,'Arthur', null);
insert into person values(null,'James',0);
insert into job values(null, 'Programmer')
insert into job values(null, 'Manager')
insert into job_person values(0,0);
insert into job_person values(0,1);
insert into job_person values(1,1);

我想创建一个删除语句，根据 PERSON.PERSON_ID 从 JOB 中删除孤儿（如果特定作业的连接表中只存在一个条目）。

在伪语言中： 

delete from job where job_person.job_id=job.job_id 
AND count(job_person.job_id)=1 AND job_person.person_id=X

其中 X 是一些 person_id。我尝试了很多不同的方法；我认为这是导致问题的“COUNT”部分。我是 SQL 菜鸟，所以任何帮助将不胜感激。

4

2 回答 2

2

我不跟。

由于您的 FK 约束，您不能删除JOB具有行（甚至是一个）的行。JOB_PERSON因此，无法JOB根据行删除PERSON行。

JOB_PERSON必须先删除行，然后才能删除 aJOB或PERSON可以删除​​。

如果要删除所有JOB没有 no 的行JOB_PERSON，那么一种方法是：

DELETE FROM JOB
WHERE JOB_ID NOT IN (
    SELECT JOB_ID
    FROM JOB_PERSON
)

如果要删除JOB_PERSON特定人员的所有行，然后删除所有孤儿，请分两步执行：

DELETE FROM JOB_PERSON
WHERE PERSON_ID = X

DELETE FROM JOB
WHERE JOB_ID NOT IN (
    SELECT JOB_ID
    FROM JOB_PERSON
)

如果您只想删除JOB以前链接到 X 的孤儿，则需要在第一次删除之前将它们保存在临时表中。

INSERT INTO TEMP_TABLE
SELECT JOB.JOB_ID
FROM JOB
INNER JOIN JOB_PERSON
    ON JOB_PERSON.JOB_ID = JOB.JOB_ID
WHERE JOB_PERSON.PERSON_ID = X

DELETE FROM PERSON
WHERE PERSON_ID = X

-- YOUR CASCADING DELETE DOES THIS:
/*
DELETE FROM JOB_PERSON
WHERE PERSON_ID = X
*/

-- Now clean up (only) new orphans on the other side
DELETE FROM JOB
WHERE JOB_ID NOT IN (
    SELECT JOB_ID
    FROM JOB_PERSON
)
AND JOB_ID IN (
    SELECT JOB_ID
    FROM TEMP_TABLE
)
于 2008-11-07T14:34:04.623 回答
1

这将从您的表 JOB 条目中删除，这些条目在表 JOB_PERSON（Orpheans）中没有条目。

DELETE FROM JOB
WHERE JOB_ID NOT IN (
    SELECT JOB_ID
    FROM JOB_PERSON
)

您不能删除由其他表上的外部链接的行...

于 2008-11-07T14:36:23.387 回答