sql - 如何确保非负列？

Question

我需要创建一个Branch包含列branch_name和branch_city字符类型的表，assets作为整数类型。branch_name是主键，我必须确保它assets是非负数。

我试过了

CREATE TABLE Branch
(
    branch_name navarchar(100) primary key,
    branch_city nvarchar(100),
    assests int NOT NULL
)

Answer 1

您需要为您的主键定义一个数据类型，并且您需要添加一个CHECK约束以确保assets它是非负的：

CREATE TABLE dbo.Branch
(
    branch_name NVARCHAR(100) primary key,
    branch_city nvarchar(100),
    assets int NOT NULL CHECK (assets >= 0)
)

Answer 2

更改表创建约束以检查列

ALTER TABLE Branch ADD CONSTRAINT chkassets CHECK (assets > 0);

Answer 3

试试这个

CREATE TABLE Branch (
    branch_name VARCHAR(100) PRIMARY KEY
    ,branch_city NVARCHAR(100)
    ,assests INT NOT NULL
    ,CONSTRAINT ck_assets_positive CHECK (assests >= 0)
    )