SQL Server: ALTERTABLEPersons ADDCONSTRAINTdf_City DEFAULT'Sandnes'FOR City; MS Access: ALTERTABLEPersons ALTERCOLUMNCitySETDEFAULT'Sandnes'; Oracle: ALTERTABLEPersons MODIFYCityDEFAULT'Sandnes'; DROP a DEFAULT Constraint To drop aDEFAULTconstraint, use the following SQL: MySQL: ALTERTABLEPersons ALTERCityDROPDEFAULT; SQL Server / Oracle / MS Access: ALTERTABLEPersons ALTERCOLUMNCit...
-- 1.员工id:添加主键约束primary key eid varchar(20) primary key, -- 2.员工名字:添加非空约束not null,唯一约束unique ename varchar(20) not null unique, -- 3.员工性别与年龄:添加检查约束check sex char(2) check(sex in ('男','女')), age number(3) check(age>0), -- 4.员工工资:添...
【说站】mysql中default的使用 1、用于设置列的默认值,如果没有为某个字段赋值,系统会自动为该字段插入默认值。 没赋值指的是,当insert插入数据时,该字段没有指明。 2、如果指定空值,则存储的最终值是空值。 实例 代码语言:javascript 代码运行次数:0 mysql>create tableuser(ageint(11)default18);QueryOK,0row...
CREATE TABLE student( id INT PRIMARY KEY, -- 主键 NAME VARCHAR(20) ) 1. 2. 3. 4. 5、自增长 -- auto_increment 作用:自动递增。 示例: CREATE TABLE student( id INT(4) ZEROFILL PRIMARY KEY AUTO_INCREMENT, -- 自增长,从0开始 ZEROFILL 零填充 NAME VARCHAR(20) ) 1. 2. 3. 4. 注意...
An item with the same key has already been added An item with the same key has already been added. An TLS 1.0 connection request was received from a remote client application, but none of the cipher suites supported by the client application are supported by the server. The SSL connection ...
PRIMARY KEY (ID) ); CREATE TABLE Descriptions ( ID INT(4) NOT NULL, Language VARCHAR(2) NOT NULL, Description TEXT NOT NULL, PRIMARY KEY (ID, Language) ); Now i assume English being default language. For example i want to choose description for book with ID = 1001 AND Language = '...
PRIMARY KEY (st_no))//定义st_no学号为主键。 例:要建立课程设置表(subject) CREATE TABLE subject//创建基本表subject (su_no CHAR(4) NOT NULL,// 定义列su_no课号,类型为4位定长字符串,非空 su_subject CHAR(20) NOT NULL,// 定义列su_subject课程名,类型为20位定长字符串,非空 ...
SQL CREATETABLEdbo.test (idINTidentity(1,1)NOTNULLCONSTRAINTPK_test PRIMARYKEY,date_inserted DATETIMEOFFSET(2)NOTNULLCONSTRAINTDF_test_date_insertedDEFAULT(sysdatetimeoffset()) ); A default constraint doesn't change when the row is updated. To update a value whenever the row is modified, cons...
Article for:SQL Server▾ Query below lists all table (and view) constraints - primary keys, unique key constraints and indexes, foreign keys and check and default constraints. Do you need a fortune teller to tell you about the data you have?
Customize cursor and key behaviors Use the following options to set the cursor behavior when you use certain keys. For information about how to set language-specific cursor behavior, see the Cursor movement section at Set options for language specific display later in this article. ...