Monday 26 December 2011

Dynamic Sorting in SSRS

Introduction

Many times while developing any report we come across a situation where we need to SORT the TABLE columns or the columns in the GROUP dynamically. There are many well known ways to achieve this. However, here I will demonstrate a not-so-known way -

 Implementation

Assuming that the sorting is to be done on 3 columns – Col1,Col2 & Col3. But the ORDER is undecided until runtime. Now, what we can do is -

  1. Define 3 Report parameters. Say - @SortCol1Name,@SortCol2Name & @SortCol3Name of STRING type.
  2. Pass the name of the columns which need to sorted in the required order. Say -
    • @SortCol1Name = “ColumnX”,@SortCol2Name = “ColumnY” and @SortCol3Name = “ColumnZ”
    • OR @SortCol1Name = “ColumnY”,@SortCol2Name = “ColumnZ” and @SortCol3Name = “ColumnX”
    • OR any preferred order
  3. In the Sorting Option of the Properties dialog box of Table or Group, set the sort expression as under -
    • =Fields(Parameters!SortCol1Name.Value).Value
    • =Fields(Parameters!SortCol2Name.Value).Value
    • =Fields(Parameters!SortCol3Name.Value).Value

1

This finally gets converted to –Fields!ColumnX.Value,Fields!ColumnY.Value & Fields!ColumnZ.Value if we have the passed the following values for the parameters - @SortCol1Name = “ColumnX”,@SortCol2Name = “ColumnY” and @SortCol3Name = “ColumnZ”

Conclusion

With this trick, we can easily set the sort expression dynamically. However, there is a limitation that we can not set the Sort Direction dynamically. I could not find out a way for it. If you have any trick to get it done with this, please leave your suggestion as a comment to this post.

Thursday 15 December 2011

Tips and Tricks: Clipboard Ring and Toolbox Snippets


Introduction

Today I show you my favorite future in visual studio which is Clipboard Rind and Toolbox Snippets.

Implementation

1.    Clipboard Ring

Many times I wish I could go back to something I copied & pasted just a few minutes ago, then to have to go and copy the same text all over again. Turns out that Visual Studio already has this “hidden” feature.  It’s called the Clipboard Ring

If you copy a number of items to the clipboard, pressing [Ctrl] + [Shift] + [V] will paste the last text that was copied, but it will also highlight the pasted phrase.

Continue holding down [Ctrl] + [Shift] and press [V] again.  This will cause that highlighted section to cycle through the other items on the clipboard.  This is extremely useful when you have to copy multiple lines of separate text to a new document. 

You can also use [Ctrl] + [Shift] + [Insert] keys instead of [Ctrl] + [Shift] + [V]

2.     Toolbox Snippets

Now, you might be saying, “Great, but what if I want to save a piece of code that I use frequently in multiple places? It means same pieces of code change in multiple files. I don’t want to have to cycle through the clipboard ring every time.”  Well, there’s also a feature for that

If you highlight a section of code (or text) and drag it to the Toolbox, VS will create a "snippet” (not to be confused with code snippets). When u want back that code then you dragged into the VS editor or double click on that snippet it will paste in VS editor.

And last but not least these snippets also available in next day.

Screen Sot


Wednesday 7 December 2011

How many times the T-SQL inside the CTE is executed?

Introduction

Common Table Expression (CTE) has become very popular these days. However, many users of CTE still have a myth that the t-sql written inside the CTE will be executed only once irrespective of the number of times it is referred in the subsequent CTEs or the related query.

However, this is not correct. It is a pure misconception. And let’s try to prove this with a simple example.

 Proof

The Query 

;WITH CTE1 AS (
SELECT 
  * 
FROM 
  dbo.Employees
),CTE2 AS (
SELECT 
  * 
FROM 
  CTE1
)
SELECT
  C1.EmployeeID,
  C1.Name,
  C2.EmployeeID,
  C2.Name,
  C3.EmployeeID,
  C3.Name
FROM
  CTE1 C1
INNER JOIN CTE2 C2
  ON C2.EmployeeID = C1.EmployeeID
INNER JOIN CTE1 C3
  ON C3.EmployeeID = C1.EmployeeID

 


Execution Plan


CTE


 


Please have a look at the execution plan. It clearly shows that even though the t-sql to fetch the data from the table is written only once inside CTE1, the Scan is done thrice. This is because CTE1 is referred thrice in the final query -



  1. Two times CTE1 is directly used.
  2. Once CTE1 is used indirectly via CTE2.

 Conclusion


The CTE should be thought of a view that is defined for the current query only. At the time of execution, the query optimizer will replace all the direct/indirect use of CTE with the actual query in the same way as it does for Views.

Friday 2 December 2011

Workarounds for SSRS 2008 Font rendering issue

 

Problem

A report developed using SSRS 2008 either through Visual Studio 2010 or BIDS 2008 does not renders properly when viewed in the Report Viewer 10.0 via Remote Desktop or any 3rd party applications using Terminal Services in the background.

Remote Rendering

vs2010remote

Local Rendering

vs2010local

Workarounds

  1. Change the Screen Resolution to 1024 X 768 or any 4:3 aspect ratio for both the Remote machine as well as the local machine.
  2. Export the report as PDF and then take the print outs if required.
  3. If the above two solutions does not work for you, unfortunately you will have to look back to SSRS 2005.

Hope, this saves you some time of searching.

Wednesday 30 November 2011

Using OFFSET and FETCH

 

Introduction

Many times while developing our applications we feel the need of pagination, where our User Interface (UI) has to list a number of records and fetching them all at once and listing is not a feasible option because of the following reasons -

  1. High utilization of the network bandwidth which if on a higher side might even choke up the bandwidth.
  2. User is not guaranteed to see the latest details in a multi user environment.
  3. High need of RAM on local machine for caching/processing.

So, the solution which is generally implemented in this situation was to fetch only the relevant records from the backend. Until Denali the following were the options used to counter this situation -

  1. Before SQL 2005 – ORDER BY clause in combination with TOP
  2. From SQL 2005 onwards – ROW_NUMBER() function with a WHERE clause

And from Denali, we can use ORDER BY clause in combination with OFFSET and FETCH

Implementation

Let’s see how we can get the same output using all of the 3 ways explained above and try to fetch records from 3 to 4 assuming page size to be 2.

Total Records are as under

AllData

1. ORDER BY + TOP

DECLARE @PageNo AS INT
DECLARE @PageSize AS INT
 
SET @PageNo = 2
SET @PageSize = 2
 
SELECT
  * 
FROM (SELECT
        TOP (@PageSize) *
      FROM (SELECT 
              TOP (@PageNo * @PageSize) *
            FROM 
              dbo.DemoTable DT
            ORDER BY
              ID ASC) X
      ORDER BY
        X.ID DESC) Y
ORDER BY
  Y.ID ASC


Output


Output


 


2. ROW_NUMBER() + WHERE



DECLARE @PageNo AS INT
DECLARE @PageSize AS INT
 
SET @PageNo = 2
SET @PageSize = 2
 
;WITH Data AS (  
SELECT
  *,
  ROW_NUMBER()OVER(ORDER BY DT.ID ASC) Rno
FROM
  dbo.DemoTable DT
)
SELECT 
  ID,NAME,CITY
FROM
  Data
WHERE
  Rno BETWEEN ((@PageNo - 1) * @PageSize) + 1 AND ((@PageNo - 1) * @PageSize) + @PageSize


Output


Output


 


3. FETCH + OFFSET



DECLARE @PageNo AS INT
DECLARE @PageSize AS INT
 
SET @PageNo = 2
SET @PageSize = 2
  
SELECT 
  *
FROM 
  dbo.DemoTable DT
ORDER BY 
  DT.ID
OFFSET ((@PageNo - 1) * @PageSize)) ROWS
FETCH NEXT @PageSize ROWS ONLY
Output


Output


Performance


I did a small test using all the 3 ways and have found the Denali (OFFSET and FETCH) way the best performing one followed by the ROW_NUMBER().


 Conclusion


I would prefer using the Denali way just for 2 simple reasons -



  • Simplicity of code
  • Better performance

Remarks



  1. The Denali code is based on SQL Server Denali CTP 1 and might change after further releases.

Saturday 1 October 2011

How to find out which Table is not having rows in SQL Server?

Introduction

Many times while tuning our production databases we might try to find out the list of tables not having even a single row of data. Today, I am going to show a simple script which could be used to get a list of tables having ZERO rows.

Script

USE DBName --Change this to the DB Name you want to script for.
GO
 
DECLARE @TableRowCount TABLE
( 
    TableName VARCHAR(255), 
    RowCnt INT 
) 
   
INSERT @TableRowCount 
  EXEC sp_msForEachTable 'SELECT PARSENAME(''?'', 1),COUNT(*) FROM ?' 
 
SELECT 
    * 
FROM 
  @TableRowCount 
WHERE
    RowCnt = 0     
ORDER BY 
  RowCnt 
 
    

How to find out which Table is not having rows in SQL Server?

Introduction

Many times while tuning our production databases we might try to find out the list of tables not having even a single row of data. Today, I am going to show a simple script which could be used to get a list of tables having ZERO rows.

Script

USE DBName --Change this to the DB Name you want to script for.
GO
 
DECLARE @TableRowCount TABLE
( 
    TableName VARCHAR(255), 
    RowCnt INT 
) 
   
INSERT @TableRowCount 
  EXEC sp_msForEachTable 'SELECT PARSENAME(''?'', 1),COUNT(*) FROM ?' 
 
SELECT 
    * 
FROM 
  @TableRowCount 
WHERE
    RowCnt = 0     
ORDER BY 
  RowCnt 
 
    

Friday 30 September 2011

How to find a string value in all the string columns of a table/view in SQL Server ?

 

Introduction

I am sure many times we all might have come across situations where we need to search/find a string value in all the string columns of a given table/view in SQL Server and return the matching rows from that table.

Unfortunately, we do not have any straight forward way to do this till date AFAIK. Hence, the below script can prove to be quite handy in this situation -

USE DBName --Replace with the DB in which the table resides
GO
 
--Declare variables and initialize them
DECLARE @TableSchema AS VARCHAR(50) = 'SchemaName' --Replace this with the name of Schema of the Table/View
DECLARE @TableName AS VARCHAR(50) = 'TableName' --Replace this with the name of the Table/View to search
DECLARE @SearchString AS VARCHAR(50) = 'SearchString' --Replace this with actual SearchString
 
DECLARE @Qry AS NVARCHAR(MAX)
DECLARE @Columns AS VARCHAR(MAX)
 
--Prepare the columns
SET @Columns = STUFF((
SELECT 
  '+' + CASE WHEN IS_NULLABLE = 'YES' THEN 'ISNULL(' + C.COLUMN_NAME + ','''')' ELSE C.COLUMN_NAME END
FROM 
  INFORMATION_SCHEMA.COLUMNS C
WHERE
  C.TABLE_SCHEMA = COALESCE(@TableSchema,C.TABLE_SCHEMA)
  AND C.TABLE_NAME = COALESCE(@TableName,C.TABLE_NAME)
  AND C.DATA_TYPE IN ('CHAR','NCHAR','NTEXT','NVARCHAR','TEXT','VARCHAR')
FOR XML PATH('')),1,1,'')
 
--Prepare the Query
SET @Qry = N' SELECT ' +
            '  * ' +
            ' FROM ' +
            @TableSchema + '.' + @TableName +
            ' WHERE  ' +
              @Columns + ' LIKE ''%' + @SearchString + '%'''  
 
--Execute the Query
EXEC SP_EXECUTESQL @Qry

Please note that the above script works only for the following column types - CHAR,NCHAR,NTEXT,NVARCHAR,TEXT,VARCHAR


Njoy searching….

Monday 22 August 2011

T-SQL to find Fragmented Indexes

Fragmentation of Indexes is one of the reason for low performing queries resulting in a poor application performance.

Today, I will present a simple script which will help in identifying the level of fragmentation in a Database.

--Replace this with the name of the Database for which we want to find the fragmentation.
USE <DBName> 
GO
 
DECLARE @DBName AS VARCHAR(10) = 'DBName'
DECLARE @DBID AS INT = DB_ID(@DBName)
DECLARE @AllowedFragmentation AS INT = 70 --A acceptable value in Percent(%) for fragmentation.
DECLARE @Qry AS VARCHAR(MAX)
 
SELECT
  --@DBID [DBID],
  --@DBName DBName,
  PS.OBJECT_ID ObjectID,
  COALESCE(T.name,V.name) ObjectName,
  PS.index_id,
  I.name IndexName,
  PS.page_count AS TotalPages,
  (PS.page_count * 8)/1024.0 as TotalMB,
  ((PS.page_count * 8)/1024.0) * (PS.avg_fragmentation_in_percent/100) as ReclaimableMB,
  PS.avg_fragmentation_in_percent AvgFragmentationPercent
FROM
  sys.dm_db_index_physical_stats (@DBID, NULL, NULL, NULL, NULL) AS PS
INNER JOIN sys.indexes AS I
  ON PS.OBJECT_ID = I.OBJECT_ID
    AND PS.index_id = I.index_id  
LEFT JOIN sys.tables T
  ON T.object_id = I.object_id
LEFT JOIN sys.views V
  ON V.object_id = I.object_id
WHERE
  PS.database_id = @DBID
  AND PS.avg_fragmentation_in_percent > @AllowedFragmentation 
ORDER BY    
  PS.avg_fragmentation_in_percent DESC 

Here, I have considered 70% fragmentation as an acceptable level of fragmentation.


Hope, this helps.