Create Named CHECK Constraint It's a good practice to createnamed constraintsso that it is easier to alter and drop constraints. Here's an example to create a namedCHECKconstraint: -- create a named constraint named amountCK-- the constraint makes sure that amount is greater than 0CREATETABL...
SQL CHECK on CREATE TABLE The following SQL creates aCHECKconstraint on the "Age" column when the "Persons" table is created. TheCHECKconstraint ensures that the age of a person must be 18, or older: MySQL: CREATETABLEPersons ( ID intNOTNULL, ...
/***在创建表后添加默认约束***/--创建People表--createtablePeople( Uidintidentity(1,1)primarykey,--主键约束--Namevarchar(20)notnullunique,--唯一约束--HomeAdressvarchar(50)notnull,--默认约束--Notesvarchar(100)null)--添加默认约束--altertablePeopleaddconstraintDF_People_HomeAddressdefault'未填写'...
drop table 表名; go --创建表 create table 表名 ( --字段声明 列名int identity(1,1) not null, 列名nvarchar(50) null, 列名nvarchar(50) null constraint 约束名 check(约束规则), 列名nvarchar(50) null, 列名int, 列名int constraint 约束名 check(约束规则) primary key clustered(列名 asc) with(...
AlterTable 表名 DropConstraint 约束名 附加:在创建表的时候同时添加约束的写法: use stuDB go if exists(select *from Sysobjectswherename ='stuInfo') droptable stuInfo go createtable stuInfo ( stuNamevarchar(20)notnullprimarykey(stuName)
字段定义constraint 约束名约否类型(字段名)-->unique,primary key,check 字段定义constraint 约否名foreingn key (字段名)references 表名(字段名)--->foreign 三、建表时约束定义 1.定义各种不同的约束 --创建一个用于作外键的表tb_dept SQL> CREATE TABLE tb_dept ...
] referenced_table_name [ ( ref_column ) ] | CHECK ( logical_expression ) } <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } { NONCLUSTERED ( column_name [ ASC | DESC ] [ ,... n ]) | NONCLUSTERED HASH ( column_name [ ,... n ] ) WITH ...
字段定义constraint约束名约否类型(字段名)-->unique,primarykey,check 字段定义constraint约否名foreingnkey(字段名)references表名(字段名)--->foreign 三、建表时约束定义 1.定义各种不同的约束 --创建一个用于作外键的表tb_dept SQL>CREATETABLEtb_dept ...
基于磁盘的 CREATE TABLE 语法: syntaxsql 复制 CREATE TABLE { database_name.schema_name.table_name | schema_name.table_name | table_name } [ AS FileTable ] ( { <column_definition> | <computed_column_definition> | <column_set_definition> | [ <table_constraint> ] [ ,... n ] | [...
] referenced_table_name [ ( ref_column ) ] | CHECK ( logical_expression ) } <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } { NONCLUSTERED ( column_name [ ASC | DESC ] [ ,... n ]) | NONCLUSTERED HASH ( column_name [ ,... n ] ) WITH ...