ADD CONSTRAINT DF_Gender DEFAULT (0) FOR Gender; ``` 为`OrderInfo` 表添加外键约束和默认值约束: ```sql ALTER TABLE OrderInfo ADD CONSTRAINT FK_Userld FOREIGN KEY (Userld) REFERENCES UserInfo (Userld), ADD CONSTRAINT FK_Commodity FOREIGN KEY (Commodityld) REFERENCES CommodityInfo (Commodityld)...
you must use a table constraint instead of acolumn constraint. Setting a single column as the primary key within the column definition is called acolumn constraint. Defining the primary key (single or composite) outside of the column definition ...
主键约束(Primary Key constraint):要求主键列数据唯一,并且不允许为空。 唯一约束(Unique Constraint):要求该列唯一,允许为空,但只能出现一个空值。 检查约束(Check Constraint):某列取值范围显示、格式限制等,如有关年龄的约束。 默认约束(Default Constraint):某列的默认值,如我们的性别默认为“男”。 外键约束(...
T-SQL语句的基本概念语法 Geiling();--向上取整 Floor();--向下取整 Round(,)--四舍五入(数,小数点后位数) abs();--绝对值 sign();--测试正负与0,正返回1.0,负返回-1.0,0返回0 PI();--π:3.1415926··· Rand();--随机数 Lower();--全部转换成小写 Upper();--全部转换成大写 Str();--...
TSQL是查询SQL Server的核心,而索引则是提高查询效能的主角,如要写出高效能TSQL则无可避免需搭配正确索引,因为SQL Server需透过正确索引才可以快速有效地找到与索引键值相关数据,有了正确索引SQL Server就不需要扫描数据页(data page)上每一笔数据,而在众多查询效能调校技术中,透过建立并设计正确索引算是最基本的...
constraint Sale_Prim Primary Key(Date,BNo) ) 1. 2. 3. 4. 5. 6. 7. 8. 创建XXX通常都对应于create语句: 创建数据库:create database db_name on ... log on ... 创建数据表:create table table_name (Attributes) 创建索引:create index index_name on tb_name(Attributes) ...
GO CREATE TABLE 警员信息 (警号 Char(6) CONSTRAINT pk_JH PRIMARY KEY,姓名 nChar(8) NOT NULL,性别 nChar(4) CONSTRAINT def_XB DEFAULT '男',CONSTRAINT chk_XB CHECK(性别 in('男','女','未知')),出生日期 Datetime,省份证号 Char(18), CONSTRAINT uq_ID UNIQUE,职务...
Visit(SqlPrimaryKeyConstraint) Visit(SqlOrderByItem) Visit(SqlOptimizeForSequentialKeyIndexOption) Visit(SqlOnlineIndexOption) Visit(SqlOffsetFetchClause) Visit(SqlObjectReference) Visit(SqlObjectIdentifier) Visit(SqlNotBooleanExpression) Visit(SqlOrderByClause) Visit(SqlMul...
PRIMARY KEY constraint BTW, if you are wondering what a NULLable constraint is, it is the formal representation of a NULL / NOT NULL definition for a field. We don’t normally think of NULL definitions in that way but in the parser that is how it is represented Anyways, constraints such...
直接使用下列TSQL命令即可。 ALTER TABLE TSBDISCTEST ADD [ID] int identity 程式碼片段如下: CREATE TABLE TSBDISC2 (BSN int PRIMARY KEY) GO CREATE TABLE TSBDISCTEST (TESTSN int PRIMARY KEY, BSN int CONSTRAINT FK_TSBDISCC FOREIGN KEY REFERENCES TSBDISC2(BSN)) GO INSERT INTO TSBDISC2 VALUES...