Question

您好我正在尝试在Band属性中编写If语句但没有成功T_T。我想要做的是拥有单个字符A，B，C，D，具体取决于owner_category，Sheds和Water_Supply属性。任何帮助都会很棒^^。

CREATE TABLE Rent_Band
(
    Plot_ID NUMBER(3),
    Band VARCHAR(1)
    IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Council' AND WHERE Sheds ='No' THEN Band ='A'
    ELSE IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Private' AND WHERE  Water_Supply ='Yes' THEN Band ='D'
    ELSE IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Council' AND WHERE  Water_Supply ='No' AND WHERE Sheds ='Yes' THEN Band ='B'
    ELSE IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Private' AND WHERE Water_Supply ='No' AND WHERE Sheds ='No' THEN Band ='B'
    ELSE THEN Band = 'C',
    Rent_Charge NUMBER(4), 
    Owner_Category VARCHAR(10) CONSTRAINT Checking_Owner_Category CHECK((Owner_Category='Private') OR (Owner_Category='Council')), 
    Sheds VARCHAR(3) CHECK((Sheds='Yes') OR (Sheds='No')), 
    Water_Supply VARCHAR(3) CHECK((Water_Supply='Yes') OR (Water_Supply='No'))
)

Answer 1

在虚拟列上阅读the documentation：

CREATE TABLE Rent_Band
(
    Plot_ID NUMBER(3),
    Band VARCHAR(1) AS
       (CASE WHEN Owner_Category = 'Council' AND Sheds ='No' THEN 'A'
            WHEN Owner_Category = 'Private' AND Water_Supply ='Yes' THEN 'D'
            WHEN Owner_Category = 'Council' AND Water_Supply ='No' AND Sheds ='Yes' THEN 'B'
            WHEN Owner_Category = 'Private' AND Water_Supply ='No' AND Sheds ='No' THEN 'B'
       ELSE 'C' END),
    Rent_Charge NUMBER(4), 
    Owner_Category VARCHAR(10) CONSTRAINT Checking_Owner_Category CHECK((Owner_Category='Private') OR (Owner_Category='Council')), 
    Sheds VARCHAR(3) CHECK((Sheds='Yes') OR (Sheds='No')), 
    Water_Supply VARCHAR(3) CHECK((Water_Supply='Yes') OR (Water_Supply='No'))
)

顺便说一句，我强烈建议：

对bit和Yes使用No字段而不是Sheds / Water_Supply约束（节省了空间和间接检查限制，并直接转换为大多数应用程序语言中的布尔值）
使用Owner_Category的查找表而不是字符串约束，原因基本相同

在Oracle SQL中使用复杂IF语句

1 个答案: