xiaoyaoyou - 2009-6-24 16:24:23
主建约束：（primary key constraint）;
唯一约束：（unique constraint）；
检查约束：（check constraint）;
默认约束：（default constraint）;
外建约束：（foreign key constraint）;
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添加约束：
alter table tablename
add constraint pk_colname primary key(colname)主建约束
alter table tablename
add constraint uq_colname unique (colname)唯一约束
alter table tablename
add constraint df_colname default('地址不详')for colname 默认约束
alter table tablename
add constraint ck_colname check(colname between 12 and 15)检查约束
alter table tablename
add constraint fk_colname foreign key(colname) references tablename(colname)外建约束
建立级联更新:(access好像不支持)
ALTER TABLE tablename ADD CONSTRAINT [FK_update] FOREIGN KEY (colname ) REFERENCES tablename(colname) ON UPDATE CASCADE
建立级联删除:(access好像不支持)
ALTER TABLE tablename ADD CONSTRAINT [FK_update] FOREIGN KEY (colname ) REFERENCES tablename(colname) ON DELETE CASCADE
删除约束：
alter table tablename
drop constraint 约束名