oracleALTER用法.doc

? oracle ALTER 用法如果sql语句中有（单引号或者双引号）括的字符串，则需要同表中严格一致，不然会显示“找不到行”这个错误。?? alter语句的用法???? 需要修改结构的，就用到alter语句，方法如下：???? ALTER?TABLE语句用于修改已经存在的表的设计。?? 语法：ALTER?TABLE?table?ADD?COLUMN?field?type[(size)]?[NOT?NULL]?[CONSTRAINT?index]?? ALTER?TABLE?table?ADD?CONSTRAINT?multifieldindex?? ALTER?TABLE?table?DROP?COLUMN?field?? ALTER?TABLE?table?DROP?CONSTRAINT?indexname?? ?? 说明：table参数用于指定要修改的表的名称。?? ADD?COLUMN为SQL的保留字，使用它将向表中添加字段。?? ADD?CONSTRAINT为SQL的保留字，使用它将向表中添加索引。?? DROP?COLUMN为SQL的保留字，使用它将向表中删除字段。?? DROP?CONSTRAINT为SQL的保留字，使用它将向表中删除索引。?? field指定要添加或删除的字段的名称。??? type参数指定新建字段的数据类型。?? size参数用于指定文本或二进制字段的长度。?? indexname参数指定要删除的多重字段索引的名称。?? ?? 用sql*plus或第三方可以运行sql语句的程序登录数据库：?? ?? ALTER?TABLE?(表名)?ADD?(列名?数据类型);??? ALTER?TABLE?(表名)?MODIFY?(列名?数据类型);??? ALTER?TABLE?(表名)?RENAME?COLUMN?(当前列名)?TO?(新列名);??/////不需要括号?? ALTER?TABLE?(表名)?DROP?COLUMN?(列名);??? ALTER?TABLE?(当前表名)?RENAME?TO?(新表名);?? ?? 如：?? Alter?Table?Employ?Add?(weight?Number(38,0))?;?? ?? Alter?Table?Employ?Modify?(weight?Number(13,2))?;?? ?? Alter?Table?Emp?Rename?Cloumn?weight?To?weight_new?;?? ??????????ALTER?TABLE?emp?DROP?COLUMN?weight_new?;?? ?? ??????????ALTER?TABLE?bouns?RENAME?TO?bonus_new;?? 增加一个列：?? ALTER?TABLE?表名?ADD(列名?数据类型);?? 如：?? ALTER?TABLE?emp?ADD(weight?NUMBER(38,0));?? ?? 修改一个列的数据类型(一般限于修改长度，修改为一个不同类型时有诸多限制):?? ALTER?TABLE?表名?MODIFY(列名?数据类型);?? 如：?? ALTER?TABLE?emp?MODIFY(weight?NUMBER(3,0)?NOT?NULL);?? ?? 给列改名：?? ALTER?TABLE?表名?RENAME?COLUMN?当前列名?TO?新列名;?? 如：?? ALTER?TABLE?emp?RENAME?COLUMN?weight?TO?weight_new;?? ?? 删除一个列：?? ALTER?TABLE?表名?DROP?COLUMN?列名;?? 如：?? ALTER?TABLE?emp?DROP?COLUMN?weight_new;?? ?? 将一个表改名：?? ALTER?TABLE?当前表名?RENAME?TO?新表名;?? 如：?? ALTER?TABLE?bouns?RENAME?TO?bonus_new?? ============================================================================ alter?USER?user?IDENTIFIEDBY?’newpassword’REPLACE?’oldpassword’;?? Oracle中使用alter table来增加,删除,修改列的语法 alter table tablename add (column datatype [default value][null/not null],….); alter table tablename modify (column datatype [defau