如何从sql中的一行中选择数据作为表？

Question

I have simple table:

|   Val1    |    Val2    |
--------------------------
|    10     |     20     |
--------------------------
|    20     |     30     |
--------------------------

How to select data from one row in this and get result as table where data in first column will be column name from original table and data in second column will be data from row? Like this:

| Name | value |
----------------
| val1 | 10    |
----------------
| val2 | 20    |

Answer 1

This SQL Script will create a temporary table, insert some values and unpivot the result.

CREATE TABLE #B
   ( VAL1 INT, VAL2 INT)

INSERT INTO #B VALUES(10,20),(20,30)

SELECT * FROM #B

SELECT U.NAME, U.VALUE
FROM (SELECT * FROM #B WHERE VAL1 = 10) AS SEL
UNPIVOT
(
  VALUE
  FOR NAME IN (VAL1, VAL2)
) U;

DROP TABLE #B

You did not explicitly prescribe how to "select data from one row in this", so I added a sample WHERE clause in a sub select.

Answer 2

And another alternate solution is - using CROSS APPLY

DECLARE @temp table ([val1] int, [val2] int);

INSERT @temp (val1, val2) 
VALUES (10, 20), 
        (20, 30);


SELECT x.Name, x.Value FROM @temp
CROSS APPLY (
    VALUES ('Val1', val1),
            ('Val2', val2)
) x(Name, Value)

Result

Name    Value
-------------
Val1    10
Val2    20
Val1    20
Val2    30

Answer 3

Consider this scenario :

Table 1:

DEPARTMENT  EMPID   ENAME   SALARY
A/C     1   TEST1   2000
SALES   2   TEST2   3000

Table 2:

ColumnName  1   2
DEPARTMENT  A/C     SALES
EMPID   1   2
ENAME   TEST1   TEST2
SALARY  2000    3000

If we are required to transform result set in Table1 format to Table2 format:

How to display dynamically horizontal rows vertically:

To display dynamically horizontal rows vertically, I have used the technique of dynamic unpivoting (using Xquery and nodes() method )

and then dynamic pivoting .

Below code block will transform result set in Table1 format to Table2 format.

DECLARE @EMPLOYEE TABLE (DEPARTMENT VARCHAR(20),EMPID INT,ENAME VARCHAR(20),SALARY INT)
INSERT @EMPLOYEE SELECT 'A/C',01,'TEST1',2000
INSERT @EMPLOYEE SELECT 'SALES',02,'TEST2',3000

SELECT * FROM @EMPLOYEE

DECLARE @Xmldata XML = (SELECT * FROM @EMPLOYEE FOR XML PATH('') )  

--Dynamic unpivoting
SELECT * INTO ##temp FROM (
SELECT 
ROW_NUMBER()OVER(PARTITION BY ColumnName ORDER BY ColumnValue) rn,* FROM (
SELECT i.value('local-name(.)','varchar(100)') ColumnName,
       i.value('.','varchar(100)') ColumnValue
FROM @xmldata.nodes('//*[text()]') x(i) ) tmp ) tmp1
--SELECT * FROM ##temp

--Dynamic pivoting
DECLARE @Columns NVARCHAR(MAX),@query NVARCHAR(MAX)
SELECT @Columns = STUFF(
 (SELECT  ', ' +QUOTENAME(CONVERT(VARCHAR,rn)) FROM
 (SELECT DISTINCT rn FROM ##temp ) AS T FOR XML PATH('')),1,2,'') 
SET @query = N'
SELECT ColumnName,' + @Columns + '
FROM
(
  SELECT * FROM ##temp
)  i
PIVOT
(
  MAX(ColumnValue) FOR rn IN ('
  + @Columns
  + ')
)  j ;';

EXEC (@query)
--PRINT @query
DROP TABLE ##temp

I hope this has helped you understand your problem.