Question

I try to update a column in a temporary table by concatenating rows from another table.

Look at this:

DECLARE @Test VARCHAR(MAX);

CREATE TABLE #Test
(
     EmployeeId INT
     ,Html VARCHAR(MAX)
);

CREATE TABLE #EmployeeItems
(
    EmployeeId INT
    ,ItemNo INT
);

INSERT INTO #EmployeeItems (EmployeeId, ItemNo)
VALUES
    (1, 1)
    ,(1, 2);

INSERT INTO #Test (EmployeeId, Html) VALUES (1, '<div class="first">');
SET @Test = '<div class="first">';

UPDATE T SET Html += '<div class="second">' + CAST(E.ItemNo AS VARCHAR) + '</div>'
FROM #Test AS T
    JOIN #EmployeeItems AS E ON T.EmployeeId = E.EmployeeId;

SELECT @Test += '<div class="second">' + CAST(E.ItemNo AS VARCHAR) + '</div>'
FROM #Test AS T
JOIN #EmployeeItems AS E ON T.EmployeeId = E.EmployeeId;

UPDATE #Test SET Html += '</div>';
SET @Test += '</div>';

SELECT Html FROM #Test;
SELECT @Test;

DROP TABLE #Test;
DROP TABLE #EmployeeItems;

The column in the #Test table contains: <div class="first"><div class="second">1</div></div>

And the @Test variable contains: <div class="first"><div class="second">1</div><div class="second">2</div></div>

Why is this? What difference is it? I thought I would get the same results but in the table case it only concatenates one row, the first.

What should I do instead to update my table without running a cursor?

EDIT

My original problem comes from something like this:

My input data is

CREATE TABLE #Actions(EmployeeId INT,EmployeeName VARCHAR(100),ActionStart TIME,ActionEnd TIME,Type VARCHAR(10));
INSERT INTO #Actions(EmployeeId,EmployeeName,ActionStart,ActionEnd, Type)
VALUES (1,'Bob','09:00','12:00', 'action'),(1,'Bob','14:30','16:00', 'action'),(1,'Bob','18:00','20:00', 'event'),(2,'Susan','10:00','12:00', 'action');

I want output like this

<div class="employee" employeeid="1" employeename="Bob">
    <div class="action" start="09:00" end="12:00" type="action"></div>
    <div class="action" start="14:30" end="16:00" type="action"></div>
    <div class="action" start="18:00" end="20:00" type="event"></div>
</div>
<div class="employee" employeeid="2" employeename="Susan">
    <div class="action" start="10:00" end="12:00" type="action"></div>
</div>

Like the first example this is a simplified example. But if I solve a case I can solve my problem. How would you do this with the FOR XML clause?

Answer 1

Think of the variable concatenation as a quirk; it’s unsupported behavior that gets used a lot in code 🙂 If you want to keep using it, you could modify your UPDATE statement like so:

UPDATE t 
SET HTML = @Test
FROM #test t

An alternate method would be to use the FOR XML syntax to concatenate

CREATE TABLE #Test
    (
      EmployeeId INT
    , Html VARCHAR(MAX)
    ) ;
CREATE TABLE #EmployeeItems
    (
      EmployeeId INT
    , ItemNo INT
    ) ;
INSERT  INTO #EmployeeItems
        ( EmployeeId, ItemNo )
VALUES  ( 1, 1 )     ,
        ( 1, 2 ) ;
INSERT  INTO #Test
        ( EmployeeId, Html )
VALUES  ( 1, '<div class="first">' ) ;

UPDATE  #Test
SET     HTML+= REPLACE(REPLACE(( SELECT '|div class="second"|'
                                        + CAST(E.ItemNo AS VARCHAR) + '|/div|'
                                 FROM   #Test AS T
                                        JOIN #EmployeeItems AS E ON T.EmployeeId = E.EmployeeId
                               FOR
                                 XML PATH('')
                               ), '|div class="second"|',
                               '<div class="second">'), '|/div|', '</div>')    
UPDATE  #Test
SET     Html += '</div>' ;

SELECT  Html
FROM    #Test ;


DROP TABLE #Test ;
DROP TABLE #EmployeeItems ;  

Or (and perhaps best), just build your XML document directly.

SELECT  'first' AS "div/@class"
      , 'second' AS "div/div/@class"
      , e.ItemNo AS "div/div"
FROM    #EmployeeItems e
FOR     XML PATH('') 

Additional Answer for edited question:

BEGIN TRAN


CREATE TABLE #Actions
    (
      EmployeeId INT
    , EmployeeName VARCHAR(100)
    , ActionStart TIME
    , ActionEnd TIME
    , Type VARCHAR(10)
    ) ;
INSERT  INTO #Actions
        ( EmployeeId, EmployeeName, ActionStart, ActionEnd, Type )
VALUES  ( 1, 'Bob', '09:00', '12:00', 'action' ),
        ( 1, 'Bob', '14:30', '16:00', 'action' ),
        ( 1, 'Bob', '18:00', '20:00', 'event' ),
        ( 2, 'Susan', '10:00', '12:00', 'action' ) ; 

;
WITH    CTE
          AS ( SELECT DISTINCT
                        EmployeeID
                      , EmployeeName
               FROM     #actions
             )
    SELECT  'employee' AS "@class"
          , employeeid AS "@employeeid"
          , employeename AS "@employeename"
          , ( SELECT    'action' AS "@class"
                      , ActionStart AS "@start"
                      , ActionEnd AS "@end"
                      , Type AS "@type"
              FROM      #Actions a2
              WHERE     a2.EmployeeId = a.EmployeeID
            FOR
              XML PATH('div')
                , TYPE
            )
    FROM    cte a
FOR     XML PATH('div') 


ROLLBACK TRAN