Wednesday, January 18, 2017

Recover unsaved SQL query scripts

Imagine a situation when you are working on a query for couple of hours and suddenly your management studio is crashed or your PC is restarted and you forgot to hit the “CTRL + S” in between.  Worst nightmare of any developer.   It is always extrmely difficult to re-create the same query again.

In the past I used to go to this folder to find my unsaved sql scripts : C:\Users\YourUsername\AppData\Local\Temp

But somehow this was never realiable.  There were few occassions when I didn’t find the query I was looking for.   Few days back I came across this table valued system fuction sys.dm_exec_sql_text which can save our day from the nightmare of not saving the scripts.  More information about this function can be found on the Books Online here: sys.dm_exec_sql_text

Now striaght away jump to the query which can help us to recover the unsaved SQL query scripts from the management studio.  



Few notes:
1. You will need VIEW SERVER STATE permissions to execute this query.
2. Since there could be many queries running on the server you would like to use WHERE condition TEXT LIKE '%SOMETHING%'.  
3. You can recover the queries only till SQL Server keeps them in the memory.
4. DM_EXEC_QUERY_STATS has few more useful columns that can help you with some extra information related to your query. You may like to add them in this query.


Tuesday, November 17, 2015

SQL query to get the job error message from SSISDB

In SQL Server 2012 Microsoft did lot of enhancements in SSIS, especially by introducing the “Project Deployment Model”.  After this so many things got better in SSIS.  While there are so many good things about this change one thing started to irritate me and that is the error in the job history.  With this change we stopped getting the exact error messages in job history.  Instead, when we open the job history to check the reason for failure we see this message:
To view the details for the execution, right-click on the Integration Services Catalog, and open the [All Executions] report.
To get the exact job failure reason we need to go the Integration Services Catalog, right click on the Project name >> Reports >> Standard Reports >> All Executions.  These reports are very nice and detailed but every time going to these reports and trying to find the error is very irritating.  Sometimes too much information is not that good.  I have seen people making mistakes in reading these execution reports.  Most of the times we are interested in error messages only and not in other execution events.  Worst part is we can’t even copy the error message to quickly Google the error for solutions.  So I thought of doing something about it.  Every time I’m not going to open execution reports to see the error.
DECLARE @DATE DATE = GETDATE() - 7 -- This is to restrict the data for last 7 days, used in ON condition
SELECT O.Operation_Id -- Not much of use
,E.Folder_Name AS Project_Name
,E.Project_name AS SSIS_Project_Name
,CONVERT(DATETIME, O.start_time) AS Start_Time
,CONVERT(DATETIME, O.end_time) AS End_Time
,OM.message as [Error_Message]
,EM.Message_Source_Name AS Component_Name
,EM.Subcomponent_Name AS Sub_Component_Name
,CASE E.Use32BitRunTime
THEN 'Yes'
END Use32BitRunTime
,E.Executed_as_name AS Executed_By

FROM [SSISDB].[internal].[operations] AS O
INNER JOIN [SSISDB].[internal].[event_messages] AS EM
ON o.start_time >= @date -- Restrict data by date AND EM.operation_id = O.operation_id

INNER JOIN [SSISDB].[internal].[operation_messages] AS OM
ON EM.operation_id = OM.operation_id

INNER JOIN [SSISDB].[internal].[executions] AS E
ON OM.Operation_id = E.EXECUTION_ID

WHERE OM.Message_Type = 120 -- 120 means Error AND EM.event_name = 'OnError'
-- This is something i'm not sure right now but SSIS.Pipeline just adding duplicates so I'm removing it. AND ISNULL(EM.subcomponent_name, '') <> 'SSIS.Pipeline'
ORDER BY EM.operation_id DESC

A quick SQL query to get the exact error would be nice.   And as I expected, all the package execution logs and error messages are stored in the SSISDB internal tables.   I created below sql script to query the SSISDB to get the exact error messages:
This was simple script to get the errors from SSISDB instead of going to Integration Services Catalogs execution reports.  Though this query is still work in progress, there could be scope for performance improvement or adding more information.  I’m still understanding the tables in SSISDB.  I’ll keep on posting the updates if any.
Mangal Pardeshi

Saturday, November 14, 2015

Dynamic PIVOT in SQL

Today I’m going to show you how to write a PIVOT query when column names are dynamic.  A dynamic pivot is very necessary when you don’t know the column names or column names can change with the time or due to any other reason.  I’m not going to discuss the pros and cons of the dynamic sql or even the Pivot itself (in my opinion pivoting of data should be handled at the reporting level.).  So let see how to write a dynamic pivot query with a very simplified example.

First lets create some sample data:
-- create table
OrderID INT,
ProductName VARCHAR(50),
Quantity INT,
OrderDate DATE
-- insert some sample data
(1, 'Pen', 100, GETDATE()-1),
(2, 'Pen', 200, GETDATE()-2),
(3, 'Pen', 300, GETDATE()-3),
(4, 'Pencil', 500, GETDATE()-1),
(5, 'Pencil', 600, GETDATE()-2),
(6, 'Pencil', 400, GETDATE()-3),
(7, 'Eraser', 30, GETDATE()-1),
(8, 'Eraser', 20, GETDATE()-2),
(9, 'Eraser', 10, GETDATE()-3),
(10, 'Pen', 100, GETDATE()-4),
(11, 'Pencil', 500, GETDATE()-4),
(12, 'Eraser', 30, GETDATE()-4);
-- verify the data
FROM Orders

This is how our data looks like:
Requirement:  Now I want to Pivot this data on the column OrderDate.  I want to show the last 3 dates of OrderDates in the column and respective quantity of each Product under the Date.  Here is the expected output, though you need to remember that you will get different column names(dates) as my sample data itself is dynamic: 
Now first understand the challenges.  Our requirement is to show the last 3 days of OrderDate.  Today I’m writing this post that’s why last days are 11 Nov – 13 Nov, but tomorrow I’ll want my query to show the dates 12 Nov – 14 Nov.  It will continue to change.  Every time changing these dates in our query can be difficult/painful/irritating.   And that’s where dynamic SQL comes into the picture.  The main challenge is to get these ever changing column names and pass them into the PIVOT block without hard-coding and also into the SELECT clause.

Lets do one thing at a time.  First we will try to get the last 3 OrderDates and concatenate them in desired order and format.  For that I’m going to use XML PATH.  Note that, there could be other methods to concatenate the column names into a single variable.  Here is my code to get the column names dynamically into a variable:
DECLARE @ColumnNames VARCHAR(1000)

SELECT @ColumnNames = 
           ', ' + QUOTENAME(CONVERT(VARCHAR(10), OrderDate, 120)) 
           FROM Orders 
           WHERE OrderDate > DATEADD(DD, -4, GETDATE()) 
           ORDER BY ', ' + QUOTENAME(CONVERT(VARCHAR(10), OrderDate, 120)) DESC
           FOR XML PATH('') 
           ), 1, 2, '')
-- Just to check how we are getting the column names
PRINT @ColumnNames

Few notes on above query:
1. DISTINCT is needed because one OrderDate is appearing multiple times in the table.
2. TOP 100 is needed because I want to order the dates in the descending order. Since our query is actually a sub-query, TOP hack is needed. I put the number 100 just randomly, I could have simply used TOP 3 because I want only top 3 dates.  When you are not sure about the number of columns you can either put a relatively large number like 100 or TOP 100 PERCENT.
3. In WHERE clause I'm restricting the dates to last 3 dates from getdate() i.e. from "TODAY".
4. I'm also converting OrderDate to varchar and using the style 120 to get the dates in the desired format.  In my case I want the dates in yyyy-mm-dd, that's why the style 120.
This is how we get column names from above query: [2015-11-13], [2015-11-12], [2015-11-11]

Now here is our PIVOT query by using dynamic column names created above:
DECLARE @ColumnNames VARCHAR(1000)

-- This part is already explained above
SELECT @ColumnNames = 
           ', ' + QUOTENAME(CONVERT(VARCHAR(10), OrderDate, 120)) 
           FROM Orders 
           WHERE OrderDate > DATEADD(DD, -4, GETDATE()) 
           ORDER BY ', ' + QUOTENAME(CONVERT(VARCHAR(10), OrderDate, 120)) DESC
           FOR XML PATH('') 
           ), 1, 2, '')

-- Preparing our PVIOT query
SET @Query = 'SELECT ProductName, ' +
@ColumnNames + '
        ( SELECT ProductName
          FROM Orders
        ) AS M
         SUM( Quantity )
         FOR OrderDate IN ( '
+ @ColumnNames + ' ) 
       ) AS P
--Executing @Query to get the result


You may also like to see my other post on Pivot: PIVOT Multiple Columns in SQL Server

Mangal Pardeshi

Thursday, November 12, 2015

Fastest way to find the row count of all the tables in SQL

Let me show you 2 simple queries to find the row count of all the tables in a Database.

Some time back I shared a trick to quickly find the row count of a table in SQL Server.  Now lets take it to next level and try to get the row count of all the tables in a Database.  There are 3-4 ways to do that, but I’m going to show you only 2 very identical methods.

1. Using Catalog View sys.partitions:

Here is the script to find the row count of all the tables using sys.partitions.  If you are a normal developer, who doesn’t have high level of permissions on a production Servers, this is the best method for you to find the row count of all the tables quickly.
           ,SUM(P.ROWS) AS [RowCount]
FROM sys.partitions AS P
INNER JOIN sys.tables AS T


2. Using DMV sys.dm_db_partition_stats:

           ,SUM(S.ROW_COUNT) AS [RowCount]
FROM sys.dm_db_partition_stats AS S
INNER JOIN sys.tables AS T


Actually nothing to chose between 2 methods, they both are quite identical, performance wise also both are very same.  Only difference between them is permissions needed to execute them.  While catalog view sys.partitions requires membership in the public role.  Effectively even if you have only “read only” access on a database, you can still use the 1st method.  On the other hand it requires VIEW DATABASE STATE permission to query the sys.dm_db_partition_stats dynamic management view.  So if you are a normal developer “sometimes” it is difficult to get that level of permissions.

And yes, as I already mentioned previously there is a chance that you will get the approximate row count if statistics are not updated.  This applies to both the methods.

To know more about the views see:
1. sys.partitions
2. sys.dm_db_partition_stats

See my couple of other posts on similar topics:
1. Fastest way to find the row count of a table in SQL Server
2. Find the row count of temporary tables in SQL Server

Mangal Pardeshi

Friday, November 6, 2015

Disk space monitoring of SQL Server

Recently I was working on creating a custom dashboard to monitor the health of all the database servers.  One thing I wanted to add to the dashboard was “Available Disk Space” on the data drives of SQL Server instances.  And I thought I’m not going to get this information in any system table or DMV and I’ll need to get the disk space information via some window commands or something.  Then I came across this dynamic management function sys.dm_os_volume_stats ,  which provided the exact information I was looking for.


Returns information about the operating system volume (directory) on which the specified databases and files are stored in SQL Server. Use this dynamic management function to check the attributes of the physical disk drive or return available free space information about the directory.

Here is the script that gives you the useful information about the total and available size of attached data volumes on SQL Server instance.
SELECT DISTINCT d.logical_volume_name AS LogicalName
,d.volume_mount_point AS DriveName
,CONVERT(NUMERIC(32,2),d.available_bytes *1.00/(1048576.0 *1024 ))AS FreeSpaceInGB
,CONVERT(NUMERIC(32,2),d.Total_Bytes *1.00/(1048576.0 *1024 )) AS TotalSizeInGB
FROM sys.master_files f
CROSS APPLY sys.dm_os_volume_stats(f.database_id, f.FILE_ID) d


This script is very useful in monitoring the data volumes, tracking the growth of the data, detecting the low disk space on the data drive of SQL Server etc.  I have implemented the low disk space alert on my Servers using this script.

Mangal Pardeshi