是否有任何SQL术语只返回表格的前两个columns 没有知道字段名称？
像
这样的东西SELECT Column(1), Column(2) FROM Table_Name
或者我是否需要走很长的路才能找到列名？我该怎么做？
答案 0 :(得分：7)
您必须先获取列名称。大多数平台都支持这一点：
select column_name,ordinal_position
from information_schema.columns
where table_schema = ...
and table_name = ...
and ordinal_position <= 2
答案 1 :(得分：3)
有
declare @select varchar(max)
set @select = 'select '
select @select=@select+COLUMN_NAME+','
from information_schema.columns
where table_name = 'TABLE' and ordinal_position <= 2
set @select=LEFT(@select,LEN(@select)-1)+' from TABLE'
exec(@select)
答案 2 :(得分：1)
我一段时间写了一个存储过程来做这个确切的工作。即使在关系理论中没有技术列顺序，SSMS也不是完全关系的。系统存储插入列的顺序并为其分配ID。使用典型的SELECT *语句遵循此顺序，这就是为什么SELECT语句每次都返回相同的顺序。在实践中，SELECT *与任何东西都不是一个好主意，因为它不会在列或行方面锁定结果顺序。这就是说，我认为人们如此坚持“你不应该这样做”他们不会编写实际可以做到的脚本。事实是有可预测的系统行为，所以如果任务不是非常重要，为什么不使用它。
这个SPROC当然有注意事项并且是用T-SQL编写的，但是如果你想要返回所有具有SELECT *相同行为的值，那么这对你来说应该很容易。输入你的表名，列数，然后点击F5。它按照从左到右的顺序返回它们，就像你期望的那样。我将它限制为只有5列，但如果您需要，可以编辑逻辑。采用临时表和永久表。
EXEC OnlySomeColumns'MyTable'，3
/*------------------------------------------------------------------------------------------------------------------
Document Title: The Unknown SELECT SPROC.sql
Created By: CR
Date: 4.28.2013
Purpose: Returns all results from temp or permanent table when not knowing the column names
SPROC Input Example: EXEC OnlySomeColumns 'MyTable', 3
--------------------------------------------------------------------------------------------------------------------*/
IF OBJECT_ID ('OnlySomeColumns', 'P') IS NOT NULL
DROP PROCEDURE OnlySomeColumns;
GO
CREATE PROCEDURE OnlySomeColumns
@TableName VARCHAR (1000),
@TotalColumns INT
AS
DECLARE @Column1 VARCHAR (1000),
@Column2 VARCHAR (1000),
@Column3 VARCHAR (1000),
@Column4 VARCHAR (1000),
@Column5 VARCHAR (1000),
@SQL VARCHAR (1000),
@TempTable VARCHAR (1000),
@PermanentTable VARCHAR (1000),
@ColumnNamesAll VARCHAR (1000)
--First determine if this is a temp table or permanent table
IF @TableName LIKE '%#%' BEGIN SET @TempTable = @TableName END --If a temporary table
IF @TableName NOT LIKE '%#%' BEGIN SET @PermanentTable = @TableName END --If a permanent column name
SET NOCOUNT ON
--Start with a few simple error checks
IF ( @TempTable = 'NULL' AND @PermanentTable = 'NULL' )
BEGIN
RAISERROR ( 'ERROR: Please select a TempTable or Permanent Table.',16,1 )
END
IF ( @TempTable <> 'NULL' AND @PermanentTable <> 'NULL' )
BEGIN
RAISERROR ( 'ERROR: Only one table can be selected at a time. Please adjust your table selection.',16,1 )
END
IF ( @TotalColumns IS NULL )
BEGIN
RAISERROR ( 'ERROR: Please select a value for @TotalColumns.',16,1 )
END
--Temp table to gather the names of the columns
IF Object_id('tempdb..#TempName') IS NOT NULL DROP TABLE #TempName
CREATE TABLE #TempName ( ID INT, Name VARCHAR (1000) )
--Select the column order from a temp table
IF @TempTable <> 'NULL'
BEGIN
--Verify the temp table exists
IF NOT EXISTS ( SELECT 1
FROM tempdb.sys.columns
WHERE object_id = object_id ('tempdb..' + @TempTable +'') )
BEGIN
RAISERROR ( 'ERROR: Your TempTable does not exist - Please select a valid TempTable.',16,1 )
RETURN
END
SET @SQL = 'INSERT INTO #TempName
SELECT column_id AS ID, Name
FROM tempdb.sys.columns
WHERE object_id = object_id (''tempdb..' + @TempTable +''')
ORDER BY column_id'
EXEC (@SQL)
END
--From a permanent table
IF @PermanentTable <> 'NULL'
BEGIN
--Verify the temp table exists
IF NOT EXISTS ( SELECT 1
FROM syscolumns
WHERE id = ( SELECT id
FROM sysobjects
WHERE Name = '' + @PermanentTable + '' ) )
BEGIN
RAISERROR ( 'ERROR: Your Table does not exist - Please select a valid Table.',16,1 )
RETURN
END
SET @SQL = 'INSERT INTO #TempName
SELECT colorder AS ID, Name
FROM syscolumns
WHERE id = ( SELECT id
FROM sysobjects
WHERE Name = ''' + @PermanentTable + ''' )
ORDER BY colorder'
EXEC (@SQL)
END
--Set the names of the columns
IF @TotalColumns >= 1 BEGIN SET @Column1 = (SELECT Name FROM #TempName WHERE ID = 1) END
IF @TotalColumns >= 2 BEGIN SET @Column2 = (SELECT Name FROM #TempName WHERE ID = 2) END
IF @TotalColumns >= 3 BEGIN SET @Column3 = (SELECT Name FROM #TempName WHERE ID = 3) END
IF @TotalColumns >= 4 BEGIN SET @Column4 = (SELECT Name FROM #TempName WHERE ID = 4) END
IF @TotalColumns >= 5 BEGIN SET @Column5 = (SELECT Name FROM #TempName WHERE ID = 5) END
--Create a select list of only the column names you want
IF Object_id('tempdb..#FinalNames') IS NOT NULL DROP TABLE #FinalNames
CREATE TABLE #FinalNames ( ID INT, Name VARCHAR (1000) )
INSERT #FinalNames
SELECT '1' AS ID, @Column1 AS Name UNION ALL
SELECT '2' AS ID, @Column2 AS Name UNION ALL
SELECT '3' AS ID, @Column3 AS Name UNION ALL
SELECT '4' AS ID, @Column4 AS Name UNION ALL
SELECT '5' AS ID, @Column5 AS Name
--Comma Delimite the names to insert into a select statement. Bracket the names in case there are spaces
SELECT @ColumnNamesAll = COALESCE(@ColumnNamesAll + '], [' ,'[') + Name
FROM #FinalNames
WHERE Name IS NOT NULL
ORDER BY ID
--Add an extra bracket at the end to complete the string
SELECT @ColumnNamesAll = @ColumnNamesAll + ']'
--Tell the user if they selected to many columns
IF ( @TotalColumns > 5 AND EXISTS (SELECT 1 FROM #FinalNames WHERE Name IS NOT NULL) )
BEGIN
SELECT 'This script has been designed for up to 5 columns' AS ERROR
UNION ALL
SELECT 'Only the first 5 columns have been selected' AS ERROR
END
IF Object_id('tempdb..#FinalNames') IS NOT NULL DROP TABLE ##OutputTable
--Select results using only the Columns you wanted
IF @TempTable <> 'NULL'
BEGIN
SET @SQL = 'SELECT ' + @ColumnNamesAll + '
INTO ##OutputTable
FROM ' + @TempTable + '
ORDER BY 1'
EXEC (@SQL)
END
IF @PermanentTable <> 'NULL'
BEGIN
SET @SQL = 'SELECT ' + @ColumnNamesAll + '
INTO ##OutputTable
FROM ' + @PermanentTable + '
ORDER BY 1'
EXEC (@SQL)
END
SELECT *
FROM ##OutputTable
SET NOCOUNT OFF
答案 3 :(得分：1)
使用dynamic query的{{1}}也可以完成这项工作：
for xml path答案 4 :(得分：0)
SQL不了解列的顺序。你需要知道列名才能得到它们。
您可以查看information_schema以获取列名。例如：
SELECT column_name
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'tbl_name'
ORDER BY ordinal_position
LIMIT 2;
答案 5 :(得分：0)
您可以查询表的sysobject以查找前两列，然后动态生成所需的SQL语句。
答案 6 :(得分：0)
如果你想要一个可以反复查询的permant对象，那么为每个只返回前2列的表创建一个视图。您可以将列命名为Column1和Column2，也可以使用现有名称。
如果要在没有任何预处理步骤的情况下从任何表返回前两列，请创建一个查询系统信息的存储过程，并执行从表中返回前两列的动态查询。
答案 7 :(得分：0)
或者我是否需要走很长的路才能找到列名？我该怎么做？
手动操作非常简单 只需先运行
select * from tbl where 1=0
此语句适用于所有主要DBMS，无需任何系统目录。 这将为您提供所有列名称，然后您需要做的就是键入前两个
select colname1, colnum2 from tbl