sql 添加 删除 判断字段是否存在
- 增加字段 ??
- alter?table?docdsp?add?dspcode?char(200) ??
- 删除字段 ??
- ALTER?TABLE?table_NAME?DROP?COLUMN?column_NAME ??
- 修改字段类型 ??
- ALTER?TABLE?table_name?ALTER?COLUMN?column_name new_data_type ??
- 改名 ??
- sp_rename ??
- 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'??
- ???? [ , [ @objtype = ]?'object_type'?] ??
- ??
- ??
- ??
- ??
- ??
- if exists(select?1?from?sysobjects?where?parent_obj=object_id('tb')?and?xtype='PK') ??
- begin??
- print?'表中已经有主键,列只能做为普通列添加'??
- ??
- ??
- alter?table?tb?add?列名?int?default?0 ??
- end??
- else??
- begin??
- print?'表中无主键,添加主键列'??
- ??
- ??
- alter?table?tb?add?列名?int?primary?key?default?0 ??
- end??
- /**************************************************************************************/ ??
- ??
- 判断table1中是否存在name字段 ??
- if exists(select?*?from?syscolumns?where?id=object_id('table1')?and?name='name')?begin??
- select?*?from?people; ??
- end??
- 判断table1中是否存在name字段且删除字段
- if exists(select?*?from?syscolumns?where?id=object_id('table1')?and?name='name')?begin??
- select?*?from?people;??
- alter?table?table1?DROP?COLUMN?name
- end