Oracle

Question

所以我有以下 table:

CREATE TABLE Projects (
ID  INTEGER  CONSTRAINT ProjPK PRIMARY KEY, 
Column1 VARCHAR2(30) NOT NULL ,
Column2 VARCHAR2(10) NOT NULL ,
Column3 INTEGER NULL ,
Column4 VARCHAR2(20) NULL ,
Column5 INTEGER NOT NULL ,
Column6 INTEGER NULL ,
Column7 DATE NULL
);

我需要为 Column7 提出一个检查约束，它只允许在第 4 列和第 6 列不为 NULL 时将 Column7 更改为不同的值。

我想表达的是，如果第 4 列或第 6 列为 NULL，则第 7 列必须为 NULL，如果第 4 列和第 6 列为 NOT NULL，则分别只能为 NOT NULL。我希望这是有道理的。任何帮助将不胜感激。

Answer 1

我会说这是触发器的任务。

简化table:

SQL> CREATE TABLE projects
  2  (
  3     id        INTEGER CONSTRAINT projpk PRIMARY KEY,
  4     column1   VARCHAR2 (30),
  5     column2   VARCHAR2 (10),
  6     column3   INTEGER,
  7     column4   VARCHAR2 (20),
  8     column5   INTEGER,
  9     column6   INTEGER,
 10     column7   DATE
 11  );

Table created.

触发器：

SQL> CREATE OR REPLACE TRIGGER trg_ch7
  2     BEFORE UPDATE
  3     ON projects
  4     FOR EACH ROW
  5  BEGIN
  6     IF :old.column7 <> :new.column7
  7     THEN
  8        IF     :new.column4 IS NULL
  9           AND :new.column6 IS NULL
 10        THEN
 11           NULL;
 12        ELSE
 13           raise_application_error (
 14              -20000,
 15              'Col 7 can not be changed because cols 4 and 6 are not empty');
 16        END IF;
 17     END IF;
 18  END;
 19  /

Trigger created.

SQL>

测试：

SQL> INSERT INTO projects (id, column1, column7)
  2       VALUES (1, 'test', SYSDATE);

1 row created.

SQL>
SQL> UPDATE projects
  2     SET column7 = SYSDATE + 1
  3   WHERE id = 1;

1 row updated.

SQL>
SQL> UPDATE projects
  2     SET column4 = 'not empty'
  3   WHERE id = 1;

1 row updated.

SQL>
SQL> UPDATE projects
  2     SET column7 = SYSDATE + 2
  3   WHERE id = 1;
UPDATE projects
       *
ERROR at line 1:
ORA-20000: Col 7 can not be changed because cols
4 and 6 are not empty
ORA-06512: at "SCOTT.TRG_CH7", line 9
ORA-04088: error during execution of trigger
'SCOTT.TRG_CH7'


SQL>

Answer 2

使用定义限制的简单检查约束

alter table projects add CONSTRAINT check_null 
CHECK ( (column4 is  null and column6 is null and column7 is null) or 
        (column4 is not null and column6 is not null and column7 is not null) );

一些测试

第 7 列定义失败，第 4,6 列未定义

 INSERT INTO projects (id, column1, column7)  VALUES (1, 'fail', SYSDATE);
 --ORA-02290: check constraint (xxx.CHECK_NULL) violated

好的，因为所有列都是 NULL

  INSERT INTO projects (id, column1, column7)  VALUES (1, 'OK', null);
-- 1 row inserted.

.. 或全部定义。

  INSERT INTO projects (id, column1,column4, column6, column7)  VALUES (2, 'OK','x',1, SYSDATE);
-- 1 row inserted.

注意从不使用 触发器 如果简单的 CHECK 约束就足够了。

Oracle - CHECK 约束 - 如果不同列中的值不为空，则只允许更改列

Oracle - CHECK Constraint - Only allow column to be changed if value in different column is not null

constraints

check-constraints