为什么此SQL / DDL违反了错误的Integrity约束？

Question

因此，它向我展示了第一次插入失败的IC4，但就IC2而言，应该是最好的选择。 IC2指出“ DB专家”应该高于200，这是第一个条目！

例如，您会看到下面的插入列表中的第一项是：

INSERT INTO Employee VALUES (10, 'Gray', 'DB guru', 240);

但是IC4失败了...为什么？！

我如何指定CONSTRAINT仅适用于某些分类值，例如我在这里尝试的？我是否缺少有关CHECK实施方式的重要概念？我对SQL真的很陌生，并试图绕过这个问题：

SPOOL ddl.out
SET ECHO ON

--
-- IMPORTANT: use the names IC1, IC2, etc. as given below.
-- --------------------------------------------------------------------
/*The following DROP command is inserted for convenience so that if you need to recompile
your code, it will drop the table (if it already exists).
*/
DROP TABLE Employee CASCADE CONSTRAINTS;
DROP TABLE Dependent CASCADE CONSTRAINTS;
--
CREATE TABLE Employee
(
id INTEGER PRIMARY KEY,
name CHAR(10) NOT NULL,
rank CHAR(10) NOT NULL,
salary INTEGER NOT NULL,
/*
IC1: The rank is one of: 'DB guru', 'DB expert', or 'DB rookie'
*/
CONSTRAINT IC1 CHECK (rank IN ('DB guru', 'DB expert', 'DB rookie')),
/*
IC2: The salary of a 'DB guru' is above 200.
*/
CONSTRAINT IC2 CHECK (rank = 'DB guru' AND salary > 200),
/*
IC3: The salary of a 'DB expert' is between 80 and 220 (inclusive).
*/
CONSTRAINT IC3 CHECK (rank = 'DB expert' AND salary >= 80 AND salary <=220 ),
/*
IC4: The salary of a 'DB rookie' is less than 100.
*/
CONSTRAINT IC4 CHECK (rank = 'DB rookie' AND salary >= 100)
);
--
--
CREATE TABLE Dependent
(
empID INTEGER,
dependentName CHAR(20) NOT NULL,
relationship CHAR(20) NOT NULL,
PRIMARY KEY (empID, dependentName),
/*
IC5: empID must refer to an employee in the company. Also:
if an employee is deleted then his/her dependents must be deleted.
IMPORTANT: DO NOT declare this IC as DEFERRABLE.
*/
CONSTRAINT IC5 FOREIGN KEY (empID) REFERENCES Employee(id)
          ON DELETE CASCADE
);
--
-- ----------------------------------------------------------------
-- TESTING THE SCHEMA
-- ----------------------------------------------------------------
INSERT INTO Employee VALUES (10, 'Gray', 'DB guru', 240);
INSERT INTO Employee VALUES (20, 'Garland', 'DB guru', 190);
INSERT INTO Employee VALUES (30, 'Edison', 'DB expert', 210);
INSERT INTO Employee VALUES (40, 'Eckerd', 'DB expert', 70);
INSERT INTO Employee VALUES (50, 'Roberts', 'DB rookie', 110);
INSERT INTO Employee VALUES (60, 'Rush', 'DB rookie', 90);
SELECT * from Employee;
-- ----------------------------------------------------------------
INSERT INTO Dependent VALUES (10, 'Grace', 'daughter');
INSERT INTO Dependent VALUES (10, 'George', 'son');
INSERT INTO Dependent VALUES (60, 'Reba', 'daughter');
INSERT INTO Dependent VALUES (15, 'Dustin', 'son');
SELECT * FROM Dependent;
--
DELETE FROM Employee WHERE id = 10;
SELECT * From Employee;
SELECT * FROM Dependent;
--
SET ECHO OFF
SPOOL OFF

Answer 1

我怀疑您可以像这样使约束互斥。这可能对您有帮助：

CHECK ((rank = 'DB guru' AND salary > 200) or
       (rank = 'DB expert' AND salary >= 80 AND salary <=220 ) or
        ....