Here, you'll find everything you need to know about primary keys and why they're so important. From what they are, how they work, and what they do, it's all right here in a single guide.
If you’ve already worked with databases, then you could hardly miss the term – Primary Key (PK). And if you’re reading this series and use it to learn about databases, well, this article should give you a good overview of what the PK really is. Still, if you’re a database exp...
What is PRIMARY KEY? The primary keys are the constraints that is defined on the columns to store or get the data uniquely from the database table. In simple words, PRIMARY KEY is a constraint that applies on one or more columns which does not allow duplicate values or NULL values and ...
百度试题 题目在SQL语言中PRIMARY KEY 的作用是()。 A. 定义主键 B. 定义外键 C. 定义视图 D. 定义索引 相关知识点: 试题来源: 解析 A.定义主键 反馈 收藏
在SQL语言中,primary key的作用是()。A、定义主码B、定义外部码C、确定主码类型D、确定外部码类型搜索 题目 在SQL语言中,primary key的作用是()。 A、定义主码 B、定义外部码 C、确定主码类型 D、确定外部码类型 答案 解析收藏 反馈 分享
百度试题 题目在SQL语言中PRIMARY KEY 的作用是( ) A. 定义主码 B. 定义外部码 C. 定义处部码的参照表 D. 确定主码类型 相关知识点: 试题来源: 解析 A.定义主码 反馈 收藏
百度试题 题目在SQL语言中,primary key的作用是()。A.定义主键B.定义外键C.确定主键类型D.确定外键类型 相关知识点: 试题来源: 解析 A 反馈 收藏
SQL中,PRIMARYKEY(主键)约束用于定义基本表的外键,它是唯一确定表中每一条记录的标识符,其值不能为NULL,也不能重复,以此来保证实体的完整性。[A.项]错误
在SQL语言中PRIMARYKEY的作用是()A定义主码B定义外部码C定义处部码的参照表D确定主码类型的正确答案和题目解析
primary key constraint 1)no duplicate values 2)no null values foreign key : its a non-key attribute which derives its value from primary key of another table its used when we want to connect tables through common fields & field connecting tables should have primary key to maintain referencial...