MySQL学习笔记汇总(四)——表的约束、存储引擎、事务 常见的约束有哪些: 非空约束(not null):约束的字段不能为NULL 唯一约束(unique):约束的字段不能重复 主键约束(primary key):约束的字段既不能为NULL,也不能重复...NULL,也不能重复 主键相关的术语 主键约束 : primary key 主键字段 : id字段添加pr...
sql CREATE TABLE table_name ( column1 datatype PRIMARY KEY, column2 datatype, ... ); Powered By In this syntax, a column is defined as the PRIMARY KEY, ensuring its values are unique and not NULL. Primary keys play a crucial role in database normalization and relational integrity by...
PRIMARY KEY (OrderID), FOREIGN KEY (PersonID) REFERENCES Persons(PersonID) ); 在多个列上建立外键: To allow naming of a FOREIGN KEYconstraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQLsyntax: MySQL / SQL Server / Oracle / MS Access: CREATE TABLE ...
MySQL 9.2 supports generated invisible primary keys for any InnoDB table that is created without an explicit primary key. When the sql_generate_invisible_primary_key server system variable is set to ON, the MySQL server automatically adds a generated invisible primary key (GIPK) to any such tabl...
Primary key syntax We've already seen several examples of thePRIMARY KEYclause of theCREATE TABLEstatement. It looks like this: CREATETABLEcities(cityvarchar(255),state_idvarchar(2),zip_codevarchar(5),PRIMARYKEY(city,state_id)); After defining columns, you add aPRIMARY KEYclause with the col...
MySQL server version for the right syntax to use near 'PRIMARY KEY ('c_custk,#MySQLserver版本和使用PRIMARYKEY的正确语法MySQL是一种常用的关系型数据库管理系统,被广泛应用于各种规模的数据存储和管理。在使用MySQL时,我们经常会遇到各种语法错误和问题。本文将重
PRIMARY KEY (ID) ); To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax:CREATE TABLE Persons ( ID int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Age int, CONSTRAINT PK_Person PRI...
table of people that donate to the different organizations. I want to make OrgID in the donations table a foreign key referring to OrgID in the organizations table as the primary key. But there will be multiple entries for a given OrgID in the organizations table. What's the way around ...
Key:表示该列是否已编制索引。PRI表示该列是表主键的一部分;UNI表示该列是UNIQUE索引的一部分;MUL表示在列中某个给定值允许出现多次。 Default:表示该列是否有默认值,如果有,那么值是多少。 Extra:表示可以获取的与给定列有关的附加信息,例如AUTO_INCREMENT等。 使用where过滤数据 语法: SELECT 列名 FROM 表名 WH...
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '.'2001-08-09',25.00,5)' at line 4 mysql> INSERT INTO Passengers(PassengerID,Name,RideDate,Fare,TrainID) ...