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查询数据库中的所有数据库名:
SELECT Name FROM Master..SysDatabases ORDER BY Name
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查询当前连接(某个)数据库中所有的表名:
SELECT Name FROM SysObjects Where XType='U' ORDER BY Name
其中XType='U' 的 U = User table,代表着使用获取当前用户的表。
注意,如果上面查询出来的结果掺杂着系统表,请加上条件:AND sysstat = '83' 也就是SELECT Name FROM SysObjects Where XType='U' AND sysstat = '83' ORDER BY Name
其他参数(如:S = System table)请参考微软官方说明https://docs.microsoft.com/en-us/sql/relational-databases/system-compatibility-views/sys-sysobjects-transact-sql?view=sql-server-2017
如果链接失效,请搜索关键字【 XType='U' 】
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查询【Blog】表,字段类型为【nvarchar】的所有字段
select sys.objects.name as tableName,syscolumns.name as columnsName from syscolumns LEFT OUTER JOIN sys.objects ON syscolumns.id = sys.objects.object_id where syscolumns.xtype = '231' and sys.objects.name = 'Blog'
其中,syscolumns.xtype 的值,通过 select TypeName = name,TypeID = system_type_id from sys.types order by TypeID
或者select distinct a.xtype,b.name from syscolumns a inner join systypes b on a.xtype=b.xtype order by a.xtype
来查询得到,例如:nvarchar:231,varchar:167
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查询【UserInfo】表的【UserName】字段的“数据类型”和“长度”
select column_name,data_type,CHARACTER_MAXIMUM_LENGTH from information_schema.columns where table_name ='UserInfo' and COLUMN_NAME='UserName'
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修改【UserInfo】表的【UserName】字段的数据类型为【nvarchar(100)】
alter table UserInfo alter column UserName nvarchar(100)
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查询当前表的架构名
select schema_id, name, schema_name(schema_id) as SchemaName from sys.tables
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获取表的基本字段属性
SELECT syscolumns.name,systypes.name,syscolumns.isnullable, syscolumns.length FROM syscolumns, systypes WHERE syscolumns.xusertype = systypes.xusertype AND syscolumns.id = object_id('表名')
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查询数据库里所有的表属性
SELECT (case when a.colorder=1 then d.name else '' end) as 表名,--如果表名相同就返回空 a.colorder as 字段序号, a.name as 字段名, (case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end) as 标识, (case when (SELECT count(*) FROM sysobjects--查询主键 WHERE (name in (SELECT name FROM sysindexes WHERE (id = a.id) AND (indid in (SELECT indid FROM sysindexkeys WHERE (id = a.id) AND (colid in (SELECT colid FROM syscolumns WHERE (id = a.id) AND (name = a.name)) ))))) AND (xtype = 'PK'))>0 then '√' else '' end) as 主键,--查询主键END b.name as 类型, a.length as 占用字节数, COLUMNPROPERTY(a.id,a.name,'PRECISION') as 长度, isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0) as 小数位数, (case when a.isnullable=1 then '√'else '' end) as 允许空, isnull(e.text,'') as 默认值, isnull(g.[value],'') AS 字段说明 FROM syscolumns a left join systypes b on a.xtype=b.xusertype inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties' left join syscomments e on a.cdefault=e.id left join sys.extended_properties g on a.id=g.major_id AND a.colid = g.minor_id order by a.id,a.colorder