用sql语句添加删除修改字段.docx

1.增加字段???? alter table docdsp???? add dspcodechar(200)2.删除字段???? ALTER TABLE table_NAME DROP COLUMNcolumn_NAME3.修改字段类型???? ALTER TABLE table_name???? ALTER COLUMNcolumn_name new_data_type4.sp_rename 改名?????EXEC sp_rename [dbo].[Table_1].[filedName1], filedName2, COLUMN 更改当前数据库中用户创建对象（如表、列或用户定义数据类型）的名称。???? 语法???? sp_rename [ @objname = ] object_name ,[ @newname = ] new_name,分类信息; [ , [ @objtype =] object_type ]?????如：EXEC sp_rename? newname,PartStock5.sp_help 显示表的一些基本情况???? sp_help object_name????如：EXEC sp_help???? PartStock6.判断某一表PartStock中字段PartVelocity是否存在if????exists???? (select???? *???? from???? syscolumns???? where????id=object_id(PartStock)???? and???? name=PartVelocity)??print????PartVelocity existselse print PartVelocity notexists另法：判断表的存在性：???? select count(*) from sysobjects where type=Uand name=你的表名判断字段的存在性：???? select count(*) from syscolumns???? whereid???? = (select id from sysobjects where type=U and name=你的表名)????and???? name = 你要判断的字段名??一个小例子--假设要处理的表名为:tb--判断要添加列的表中是否有主键if exists(select 1 from sysobjects whereparent_obj=object_id(tb) and xtype=PK)beginprint表中已经有主键,列只能做为普通列添加--添加int类型的列,默认值为0alter table tb add 列名 int default0??endelsebeginprint 表中无主键,添加主键列--添加int类型的列,默认值为0altertable tb add 列名 int primary key default 0??end7.随机读取若干条记录?????? Access语法：SELECT top 10 * From 表名 ORDER BYRnd(id)?????? Sql server:select top n * from 表名 order by newid()??????mysql select * From 表名 Order By rand() Limit n8.说明：日程安排提前五分钟提醒?????? SQL:select * from 日程安排 where datediff(minute,f开始时间,getdate())59.前10条记录?????? select top 10 * form. table1 where 范围10.包括所有在 TableA 中但不在 TableB和TableC 中的行并消除所有重复行而派生出一个结果表?????? (select afrom tableA ) except (select a from tableB) except (select a from tableC)11.说明：随机取出10条数据?????? select top 10 * from tablename order by newid()12.列出数据库里所有的表名?????? select name from sysobjects where type=U13.列出表里的所有的字段名?????? select name from syscolumns whereid=object_id(TableName)14.说明：列示type、vender、pcs字段，以type字段排列，case可以方便地实现多重选择，类似select中的case。?????? se