是否有SQL语句可以返回表中列的类型?


当前回答

在oracle SQL中,你可以这样做:

SELECT
    DATA_TYPE
FROM
    all_tab_columns 
WHERE
    table_name = 'TABLE NAME' -- in uppercase
AND column_name = 'COLUMN NAME' -- in uppercase

其他回答

对于Apache Derby,如下面的答案所示:

select columndatatype from sys.syscolumns
  where referenceid = (
    select tableid from sys.systables
    where tablename = 'YOUR_TABEL_NAME'
    and columnname= 'YOUR_COLUMN_NAME')

要在上面的答案的基础上进行构建,获得列数据类型的格式与声明列的格式相同通常是很有用的。

例如,varchar(50), varchar(max), decimal(p, s)。

这允许你这样做:

SELECT 
  [Name]         = c.[name]
, [Type]         = 
    CASE 
      WHEN tp.[name] IN ('varchar', 'char', 'varbinary') THEN tp.[name] + '(' + IIF(c.max_length = -1, 'max', CAST(c.max_length AS VARCHAR(25))) + ')' 
      WHEN tp.[name] IN ('nvarchar','nchar') THEN tp.[name] + '(' + IIF(c.max_length = -1, 'max', CAST(c.max_length / 2 AS VARCHAR(25)))+ ')'      
      WHEN tp.[name] IN ('decimal', 'numeric') THEN tp.[name] + '(' + CAST(c.[precision] AS VARCHAR(25)) + ', ' + CAST(c.[scale] AS VARCHAR(25)) + ')'
      WHEN tp.[name] IN ('datetime2') THEN tp.[name] + '(' + CAST(c.[scale] AS VARCHAR(25)) + ')'
      ELSE tp.[name]
    END
, [RawType]      = tp.[name]
, [MaxLength]    = c.max_length
, [Precision]    = c.[precision]
, [Scale]        = c.scale
, [IsNullable]   = c.is_nullable
FROM sys.tables t 
JOIN sys.schemas s ON t.schema_id = s.schema_id
JOIN sys.columns c ON t.object_id = c.object_id
JOIN sys.types tp ON c.user_type_id = tp.user_type_id
WHERE s.[name] = 'dbo' AND t.[name] = 'MyTable'

使用此查询获取Schema, Table, Column,Type, max_length, is_nullable

SELECT QUOTENAME(SCHEMA_NAME(tb.[schema_id])) AS 'Schema'
    ,QUOTENAME(OBJECT_NAME(tb.[OBJECT_ID])) AS 'Table'
    ,C.NAME as 'Column'
    ,T.name AS 'Type'
    ,C.max_length
    ,C.is_nullable
FROM SYS.COLUMNS C INNER JOIN SYS.TABLES tb ON tb.[object_id] = C.[object_id]
    INNER JOIN SYS.TYPES T ON C.system_type_id = T.user_type_id
WHERE tb.[is_ms_shipped] = 0
ORDER BY tb.[Name]

我认为在Microsoft SQL Server Management Studio中最简单和最有用的方法是:

EXEC [ServerName].[DatabaseName].dbo.sp_help 'TableName'

从SQL Server 2012开始:

SELECT * FROM sys.dm_exec_describe_first_result_set( N'SELECT * FROM [my].[Table]', NULL, 0 );