在SQL中创建一个具有空约束的表，但有约束

Question

我想创建一个表值，该值大于0且可以为null。

当我在该行中创建表列

CREATE TABLE Ship 
    (
    SITE_ID   INTEGER NOT NULL, 
    Ship_CATEGORY VARCHAR2(50) CHECK (WRECK_CATEGORY IN ('Military','Government','Passenger', 'Unknown', 'Commercial')), 
    Ship_TYPE  VARCHAR2(100) , 
    Ship_TONNAGE INTEGER CHECK ((WRECK_TONNAGE>0) AND WRECK_TONNAGE IS NULL) , 
    Ship_CAUSE  VARCHAR2(100) NULL CHECK (WRECK_CAUSE IN ('Fire', 'Collision','Unknown',' Deliberate', 'Explosion',' Attack', 'Other')), 
    Ship_DATESUNK DATE NULL, 
    Ship_CONDITION VARCHAR2(50) NULL CHECK (WRECK_CONDITION IN ('Excellent', 'Moderate','Poor', 'Very Poor')), 
    CONSTRAINT SHIPWRECK_PK PRIMARY KEY (SITE_ID) 
); 

的这样做 “Ship_TONNAGE INTEGER CHECK（（WRECK_TONNAGE> 0）和WRECK_TONNAGE IS NULL）”， 当我插入空值以这一栏，它违反了约束。我如何创建我的表，因为它满足条件？而不是SHIP

CHECK ((WRECK_TONNAGE>0) or WRECK_TONNAGE IS NULL) 

你的约束引用错列，沉船*：谢谢

Answer 1

变化从and检查约束到or。试试这个定义语句：

CREATE TABLE Ship 
    (
    SITE_ID   INTEGER NOT NULL, 
    Ship_CATEGORY VARCHAR2(50) CHECK (SHIP_CATEGORY IN ('Military','Government','Passenger', 'Unknown', 'Commercial')), 
    Ship_TYPE  VARCHAR2(100) , 
    Ship_TONNAGE INTEGER CHECK ((SHIP_TONNAGE>0) or SHIP_TONNAGE IS NULL) , 
    Ship_CAUSE  VARCHAR2(100) NULL CHECK (SHIP_CAUSE IN ('Fire', 'Collision','Unknown',' Deliberate', 'Explosion',' Attack', 'Other')), 
    Ship_DATESUNK DATE NULL, 
    Ship_CONDITION VARCHAR2(50) NULL CHECK (SHIP_CONDITION IN ('Excellent', 'Moderate','Poor', 'Very Poor')), 
    CONSTRAINT SHIPWRECK_PK PRIMARY KEY (SITE_ID) 
);