SQLServer queries all database names, table names, table structures, etc.

1. Query all database names

SELECT name FROM sysdatabases

2. Query all table names in the current database without specifying a database. Just select a database and execute SQL directly.

-- 'U':所有用户表名; 'S':所有系统表名;'V':所有视图表名
SELECT name FROM sysobjects WHERE xtype='U' OR xtype='S' OR xtype='V'

3. Get the primary key field of the specified table

SELECT name AS 'PK' FROM SysColumns WHERE id=Object_Id('Table') AND colid=(SELECT TOP 1 keyno FROM sysindexkeys WHERE id=Object_Id('Table'))

4. Query all field names in the specified table

SELECT name FROM SysColumns WHERE id=Object_Id('Table_2') 

5. Query all field names and field types in the specified table

SELECT sc.name,st.name FROM SysColumns sc,systypes st WHERE sc.xtype=st.xtype AND sc.id in(SELECT id from sysobjects WHERE xtype='U' AND name='Table')

6. Obtain part of the data structure of the table

	SELECT   c.name, 
			 c.user_type_id, 
			 c.max_length,
			 c.is_nullable,
			 remark = ex.value
			 FROM sys.columns c 
			 LEFT OUTER JOIN sys.extended_properties ex ON ex.major_id = c.object_id AND ex.minor_id = c.column_id AND ex.name = 'MS_Description'
			 WHERE
			 OBJECTPROPERTY(c.object_id, 'IsMsShipped')=0 
			 AND OBJECT_NAME(c.object_id) = 'Table'
			 ORDER
			 BY OBJECT_NAME(c.object_id), c.column_id

7. SqlServer2000 obtains table structure details

SELECT  TBL.name AS '表名',
                              CONVERT(NVARCHAR(500),DSPTN.value) AS '表说明',
                               COL.column_id AS '字段序号',
                               COL.name AS '字段名',
                               CASE WHEN COL.is_identity = 1 THEN 'YES' ELSE 'NO' END AS '标识',
                               CASE WHEN PK.object_id IS NOT NULL AND PK.index_id = COL.column_id THEN 'YES' ELSE 'N0' END AS '主键',
                               TY.name AS '类型',
                               CAST(COL.max_length AS VARCHAR) AS '占用字节数',
                               CAST(COL.precision AS VARCHAR) AS '长度',
                               CAST(COL.scale AS VARCHAR) AS '小数位数',
                               CASE WHEN COL.is_nullable = 1 THEN 'YES' ELSE 'NO' END AS '允许空',
                               ISNULL(CONVERT(NVARCHAR(500), DFTCNST.definition), '') AS '默认值',
                               CONVERT(NVARCHAR(500),SCOLMS.value) AS '字段说明'
                               FROM sys.tables TBL
                               INNER JOIN sys.columns COL ON TBL.object_id = COL.object_id
                               LEFT JOIN sys.identity_columns IDCOL ON TBL.object_id = IDCOL.object_id AND COL.column_id = IDCOL.column_id
                               LEFT JOIN sys.types TY ON COL.user_type_id = TY.user_type_id
                               LEFT JOIN (
                               SELECT 
                                   name, 
                                   object_id, 
                                   index_id 
                               FROM sys.indexes 
                               WHERE is_primary_key = 1
                                     ) PK ON TBL.object_id = PK.object_id
                                    LEFT JOIN sys.default_constraints DFTCNST ON COL.default_object_id = DFTCNST.object_id
                                    LEFT JOIN sys.extended_properties SCOLMS ON COL.object_id = SCOLMS.major_id AND 
                                    COL.column_id = SCOLMS.minor_id AND 
                                    SCOLMS.name = 'MS_Description'
                                    LEFT JOIN sys.extended_properties DSPTN ON TBL.object_id = DSPTN.major_id AND DSPTN.minor_id = 0
                                    AND DSPTN.name = 'MS_Description'
                                    WHERE TBL.name = 'table'
                                    ORDER BY TBL.name, COL.column_id

8. Obtain table structure details for SqlServer2000 or above

SELECT  TBL.name AS '表名',
                              CONVERT(NVARCHAR(500),DSPTN.value) AS '表说明',
                               COL.column_id AS '序号',
                               COL.name AS '字段名',
                               CASE WHEN COL.is_identity = 1 THEN 'YES' ELSE 'NO' END AS '标识',
                               CASE WHEN PK.object_id IS NOT NULL AND PK.index_id = COL.column_id THEN 'YES' ELSE 'N0' END AS '主键',
                               TY.name AS '类型',
                               CAST(COL.max_length AS VARCHAR) AS '占用字节数',
                               CAST(COL.precision AS VARCHAR) AS '长度',
                               CAST(COL.scale AS VARCHAR) AS '小数位数',
                               CASE WHEN COL.is_nullable = 1 THEN 'YES' ELSE 'NO' END AS '允许空',
                               ISNULL(CONVERT(NVARCHAR(500), DFTCNST.definition), '') AS '默认值',
                               CONVERT(NVARCHAR(500),SCOLMS.value) AS '字段说明'
                               FROM sys.tables TBL
                               INNER JOIN sys.columns COL ON TBL.object_id = COL.object_id
                               LEFT JOIN sys.identity_columns IDCOL ON TBL.object_id = IDCOL.object_id AND COL.column_id = IDCOL.column_id
                               LEFT JOIN sys.types TY ON COL.user_type_id = TY.user_type_id
                               LEFT JOIN (
                               SELECT 
                                   name, 
                                   object_id, 
                                   index_id 
                               FROM sys.indexes 
                               WHERE is_primary_key = 1
                                     ) PK ON TBL.object_id = PK.object_id
                                    LEFT JOIN sys.default_constraints DFTCNST ON COL.default_object_id = DFTCNST.object_id
                                    LEFT JOIN sys.extended_properties SCOLMS ON COL.object_id = SCOLMS.major_id AND 
                                    COL.column_id = SCOLMS.minor_id AND 
                                    SCOLMS.name = 'MS_Description'
                                    LEFT JOIN sys.extended_properties DSPTN ON TBL.object_id = DSPTN.major_id AND DSPTN.minor_id = 0
                                    AND DSPTN.name = 'MS_Description'
                                    WHERE TBL.name = 'table'
                                    ORDER BY TBL.name, COL.column_id