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SQL angustiis

1. Description

Conceptus: Coactus sunt regulae, quae agunt de agris in tabula ad circumscribendos notitias in mensa repositas.

Propositum: Ut accuratio, validitas et integritas notitiarum in datorum datorum curent.

2. Ritus

Auto-incrementum: auto_increment

MySQL

ALTER TABLE my_table MODIFY id INT AUTO_INCREMENT;
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SQLServer

-- 删除依赖于id列的约束
ALTER TABLE my_table DROP CONSTRAINT <constraint_name>;

-- 修改字段为自增
ALTER TABLE my_table ALTER COLUMN id INT IDENTITY(1,1);

-- 重新创建约束（如果有）
ALTER TABLE my_table ADD CONSTRAINT <constraint_name> PRIMARY KEY (id);
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addens angustia

-- 1、添加主键
ALTER TABLE 表名 ADD CONSTRAINT 主键名 PRIMARY KEY (主键字段名);
-- 例：ALTER TABLE Orders ADD CONSTRAINT FK_Orders_Customers FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID);
-- 2、添加外键
alter table 表名 add constraint 外键名 foreign key (外键字段名) references 主表(主字段名);
-- 删除外键
alter table 表名 drop foreign key 外键名;
-- 3、添加唯一约束
ALTER TABLE 表名 ADD CONSTRAINT 约束名 (需要约束的字段);
-- 4、添加默认约束
ALTER TABLE 表名 ADD CONSTRAINT 约束名 DEFAULT '默认值' FOR 字段名;
-- 5、检查约束
ALTER TABLE 表名 ADD CONSTRAINT 约束名 CHECK (Age >= 18 检查的条件);
-- 6、非空约束
ALTER TABLE 表名 ALTER COLUMN 字段名 varchar(255) NOT NULL;
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Munus claves exterarum：
Ut integritas data servetur, ager clavis externus puer mensa dicitur, et mensa apposita parentis mensa appellatur.
Delere ac update mores：

• nulla actio (default): Cum delendo/adaequationis congruum recordum in tabula parente, si recordum clavem alienam habet,Non potest renovari / delere.
• Cascade: Cum delendo/adaequationis testimonium correspondentem in mensa parente, si recordum habet clavem alienam,Delete/renovatio monumenta in subtilissima.
• nullum posuit: Cum delendo/adaequationis testimonium correspondentem in mensa parente, si recordum habet clavem alienam,Deinde valorem key extraneum in subtable nullis.
• defaltam statuto: Cum tabula parentis mutatur, columna clavis extera in tabula infantis creata ad valorem defaltae ponitur (non sustinetur ab InnoDB).

# 指定行为
alter table 表名 add constraint 外键名 foreign key (外键字段) references 主表(主字段名) on update cascade on delete cascade;
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