alter table tablename add 字段名 属性 详细的语法如下 ALTER TABLE TableName1 ADD | ALTER [COLUMN] FieldName1 FieldType [(nFieldWidth [, nPrecision])] [NULL | NOT NULL] [CHECK lExpression1 [ERROR cMessageText1]] [DEFAULT e Expression1] [PRIMARY KEY | UNIQUE] [REFERENCES TableName2 [TAG TagName1]] [NOCPTRANS] [NOVALIDATE]
Alter table tablename add 字段名 字段类型[约束] 如:ALTER TABLE EMPLOYEER ADD STARDATE DATE NOT NULL, VESTINGDATE DATE NULL 同样可以从表中删除列 ALTER TABLE TABLENAME DROP COLUMNNAME
详细的语法如下
ALTER TABLE TableName1 ADD | ALTER [COLUMN] FieldName1 FieldType
[(nFieldWidth [, nPrecision])] [NULL | NOT NULL]
[CHECK lExpression1 [ERROR cMessageText1]] [DEFAULT e Expression1]
[PRIMARY KEY | UNIQUE] [REFERENCES TableName2 [TAG TagName1]]
[NOCPTRANS] [NOVALIDATE]
如:ALTER TABLE EMPLOYEER
ADD
STARDATE DATE NOT NULL,
VESTINGDATE DATE NULL
同样可以从表中删除列
ALTER TABLE TABLENAME DROP COLUMNNAME