Wednesday, January 18, 2012

SQL Server - Create Alter Table Statements quickly

This is a follow-up to my post for listing all columns with a specific data type.

The goal of the query below is the quickly create all the needed Alter Table statements for the new user defined data type that I'm going to be replacing the old one with.

As stated previously, we are planning on upgrading an older SQL Server 2005 server to SQL Server 2008.  In the process we determined that a couple of the columns would need to have their User Defined Data Types updated.

Instead of manually coding the Alter statements, I spent a few minutes creating a select statement that would allow me to copy the results to another SQL window with all the code needed to make the change.

In the process; I like my code to look pretty, oh so pretty.  So I'm using a couple of replicate statements to pad out spaces for the code to be created.

-- Get the Maximum TableName Length for the specificed type I'm going to update
DECLARE @MaxTableName int
    SET @MaxTableName = (
                            SELECT MAX(LEN(o.Name))

                            FROM sys.columns AS c
                            JOIN sys.types   AS t ON c.user_type_id=t.user_type_id
                            JOIN sys.tables  AS o ON c.Object_id = o.Object_ID
                            Where = 'Date'
                                and t.is_user_defined = 1
                                and o.Type = 'U'

-- Get the Maximum Column Name length for the type I'm going to update
DECLARE @maxColumnName int
    SET @MaxColumnName =
                            SELECT MAX(LEN(c.Name))

                            FROM sys.columns AS c
                            JOIN sys.types   AS t ON c.user_type_id=t.user_type_id
                            JOIN sys.tables  AS o ON c.Object_id = o.Object_ID
                            Where = 'Date'
                                and t.is_user_defined = 1
                                and o.Type = 'U'

-- Now create the pretty Alter statements

-- Will just need to copy the results to a new sql window and
-- you will have all the code needed to fix your problem
            SELECT ( 'ALTER TABLE dbo.['
                            + RTRIM(LTRIM(o.Name))
                            + ']'
                            + REPLICATE (' ',@MaxTableName-LEN(o.Name))
                            + ' ALTER COLUMN ['
                            + RTRIM(LTRIM(c.Name) )
                            + ']'
                            + REPLICATE (' ',@MaxColumnName-LEN(c.Name))
                            + ' DateTime NULL'

            FROM sys.columns AS c
            JOIN sys.types   AS t ON c.user_type_id=t.user_type_id
            JOIN sys.tables  AS o ON c.Object_id = o.Object_ID
            Where = 'Date'
                and t.is_user_defined = 1
                and o.Type = 'U'
            ORDER BY c.OBJECT_ID

So using the above code I got the resulting output:

ALTER TABLE dbo.[Test1]  ALTER COLUMN [Date1]   DateTime NULL
ALTER TABLE dbo.[Test1]  ALTER COLUMN [Date20]  DateTime NULL
ALTER TABLE dbo.[Test11] ALTER COLUMN [Date300] DateTime NULL
ALTER TABLE dbo.[Test11] ALTER COLUMN [Date4]   DateTime NULL
ALTER TABLE dbo.[Test11] ALTER COLUMN [Date50]  DateTime NULL

SQL Server - List all columns with a specific data type

We are in the process of upgrading an old server from SQL Server 2005 to SQL Server 2008.  In the preliminary investigation stage we discovered that there  are a couple User Defined Data Types that are named "Date" and "Time".

As these are now system data types we needed to determine which tables and columns would be affected by the upgrade.

Come to find out, this was a pretty simple task.  Using the system tables; Objects, Columns and Types we were able to pull a list together very quickly of the tables and columns that needed to be updated:

-- Select all Columns which have the user defined type name of 'Date'
         SCHEMA_NAME(t.schema_id) AS SchemaName
        ,o.Name                   AS TableName
        ,o.Type_Desc              AS TableDescription
        ,o.Type                   AS TableType
        ,c.Object_id              AS ColumnObjectID 
        ,                   AS ColumnName

        ,                   AS TypeName
    FROM     sys.columns AS c
        JOIN sys.types   AS t ON c.user_type_id = t.user_type_id
        JOIN sys.objects AS o ON c.Object_id    = o.Object_ID
    Where            = 'Date'  -- Type Name here
        and t.is_user_defined = 1       -- Yes, we want User Data Types only
        and o.Type            = 'U'     -- User Table Types only


Well, we had a gotcha here...  The system not only saves which tables and columns that link to the UDT but all Indexes, Statistics, Stored Procedures, functions and views point to the UDT.  To see all affected types just comment out the last AND statement in the above script.

What we ended up having to do was

  • Create new UDT
    • You can not just change a UDT, it has to be created and old one dropped
    • Also means new UDT can not have same name, of course you could get creative here and add a couple of steps to the process so as to retain the same name.
  • Dropping the Statistics
  • Disabling and in some cases having to drop the individual indexes involved
  • Then Altering the table
  • Rebuilding or recreating the indexes
  • Recreate the statistics
  • Recompile the Stored Procedures and UDF's
  • Recreate any affected Views
  • Then you can drop the old UDT

It was strange, even though they still point to the 'date' UDT the functions still worked.

Seems to me, that the the UDT's aren't accomplishing their main objective and that is making it easier to maintain consistency across tables.

For example:

You have a Social Security Number of 11 digits (9 digits plus the two dashes).  You created a UDT for SSN of char(11).  This would allow you to have any tables with a SSN in it to be marked with this UDT and make sure that all are a consistent 11 digits.

Now, the government decides that they need to add a couple more digits to the mess.  So we are tasked with finding and updating all SSN to this new length format.  The UDT makes this very simple to locate all affected columns.

But, updating this column isn't as simple as changing the UDT.  Instead, you have to some major changes through out the database(s).

Monday, January 16, 2012

SQL Server - Check to see if a table is locked

How to check to table locking in SQL Server 2008 R2.

We used to use SP_LOCK and SP_LOCK2, but have since learned that the recommend method to determine locks is the code below as the two procs are to be deprecated in future releases.

Microsoft says the better way is to use the sys.dm_tran_locks dynamic management views.

The following code will select from the sys.dm_tran_locks and sys.partitions system tables.

More information on Locks can be found at the following Microsoft library pages:

Lock Modes

Locking Granularity

Key Range Locking 

--  Code to find out what table is locked and the lock reason
    object_name(P.object_id) as TableName
    , resource_type
    , resource_description
    , request_mode
                    WHEN 'S'        THEN 'Shared'
                    WHEN 'U'        THEN 'Update'
                    WHEN 'X'        THEN 'Exclusive'
                    WHEN 'IS'       THEN 'Intent Shared'
                    WHEN 'IU'       THEN 'Intent Update'
                    WHEN 'IX'       THEN 'Intent Exclusive'
                    WHEN 'SIU'      THEN 'Shared Intent Update'
                    WHEN 'SIX'      THEN 'Shared Intent Exclusive'
                    WHEN 'UIX'      THEN 'Update Intent Exclusive'
                    WHEN 'BU'       THEN 'Bulk Update'
                    WHEN 'RangeS_S' THEN 'Shared Range S'
                    WHEN 'RangeS_U' THEN 'Shared Range U'
                    WHEN 'RangeI_N' THEN 'Insert Range'
                    WHEN 'RangeI_S' THEN 'Insert Range S'
                    WHEN 'RangeI_U' THEN 'Insert Range U'
                    WHEN 'RangeI_X' THEN 'Insert Range X'
                    WHEN 'RangeX_S' THEN 'Exclusive range S'
                    WHEN 'RangeX_U' THEN 'Exclusive range U'
                    WHEN 'RangeX_X' THEN 'Exclusive range X'
                    WHEN 'SCH-M'    THEN 'Schema-Modification'
                    WHEN 'SCH-S'    THEN 'Schema-Stability'

        ELSE NULL

FROM   sys.dm_tran_locks   AS L
       join sys.partitions AS P
        on L.resource_associated_entity_id = p.hobt_id

Thursday, January 12, 2012

Write Function in SQL Server 2005

Something cool I just ran across today.  It appears that in SQL 2005 they added the 'Write' function.

This allows you to update character column, including that with the size of MAX.  This is useful as STUFF didn't work with varchar(max).

-- Create a Temp table to hold our text
        myText NVARCHAR(MAX)

-- Insert sample text we want to mess with
Select 'This a very cool Test!'

-- Use the Write function to put the text 'Hello Test'
-- at the beginning of the field
UPDATE #tmpTable
    SET myText.write(
                        'Hello Test'
                        ,0              -- Start index
                        ,0              -- Number of characters to replace

-- Show that the text has indeed been pushed to the front of the field
select * FROM #tmpTable

-- Now lets use the Write function to delete the first ten characters
UPDATE #tmpTable
    SET myText.Write(
                        ''              -- An Empty String
                       , 0              -- Start at 0
                       , 10             -- The number of characters to replace


Tuesday, January 10, 2012

SQL Server Agent System Stored Procedures

A followup post to Sql Server Agent Tables.

In addition to the tables, the are already system stored procedures that will get the information for you.  I've included some of the man arguments.  More information on the stored procedures can be seen at the Microsoft msdn link.

  • sp_help_job
    • if you run this by itself it will show all your jobs
    • Arguments:Or you can Pass in the @job_id or @job_name 
  • sp_help_jobActivity
    • shows the status of the job run.  
    • Arguments:  @job_ID or @job_Name
  •  sp_help_jobHistory
    • shows all the history information for all of the job runs
    • Arguments:  @job_ID or @job_Name
  • sp_help_jobCount
    • Arguments: @schedule_id or @Schedule_name 
    • it will return a count o how many jobs a schedule is tied to.
  • sp_help_jobs_in_schedule
    • Arguments: @schedule_id or @Schedule_name 
    • it will return a a list of all jobs tied to that schedule.sp_help_job_schedule
  • sp_help_jobSchedule
    • Shows jobs that are linked to a schedule
    • Arguments: @job_id or @job_name
  •  sp_help_jobServer
    • Shows information about server tied to a job
    • Arguments: @job_id or @job_name
  • sp_help_jobStep
    • Shows information about steps tied to a job
    • Arguments: @job_id or @job_name
  • sp_help_jobStepLog
    • Shows information about a specific job steplog
    • Arguments: @job_id or @job_name 
    •                  @step_id or @step_name
  • sp_help_schedule
    •  Shows information for schedule
    • Pass in the @schedule_id or @Schedule_name or no parameters for all

Saturday, January 7, 2012

Sql Server Agent Tables

SQL Server stores the SQL Server Agent Jobs in various tables in the msdb.  This provides you an easy way to view jobs, their steps as well as their run history.

  • sysJobs
    • Stores the name, job_ID and related information
  • sysJobSchedules
    • Shows the schedules for the jobs
    • Arguments: Uses Job_ID to link to sysJobs
  • sysJobSteps
    • Shows each step in a job.  Includes the command (actual code used), database and related information
    • Arguments: Uses job_id to link to sysJobs
  •  sysJobHistory
    • Shows the  run history for that job, status, date, run time and duration to complete
    • Arguments: Uses Job_ID and step_ID
  • sysJobServers
    • Stores server related information for jobs
  • sysJobActivity
    • Stores data about the job activity
  • sysJobStepsLogs
    • If it is enabled, it will show specific job step information

Code used to get various information:
use msdb

DECLARE @jobID varchar(50)

-- Get the jobID for a specific job
SET @jobID = ( select job_ID FROM sysJobs where name = 'ETL_Test' )

-- Get the job Information
SELECT * FROM sysJobs     where job_id = @jobID

-- Get the steps for that job
Select * from sysJobSteps where job_id = @jobID order by step_id

-- Show all jobs that use the storedProcedure xs_myTest
SELECT * FROM sysJobSteps where command like '%xs_myTest%'

In addition to the tables there are also System Stored Procedures.  

SQL Server: how to delete a table in chunks

I was asked the other day how someone should delete all of rows in a very large table when they couldn't use the TRUNCATE function because there were foreign keys tied to that table.

Deleting all the tables in a single step could cause a large transaction and cause lots of locks.

I found the code below a while back on a better way to minimize the maximum locks and resources on the server.  Deleting in smaller chunks creates a bunch of small transactions that is more manageable for the server to handle.

In addition, if you happen to have an error on one of the chunks, all the deletes up to then are retained and not rolled back, only that one chunk is rolled back.   Then again, if you have an error, all prior deletes are not recoverable.

For this example I'll create a table, populate it with a small set of tables, then the delete command is what we actually use to delete it in chunks.

--- Create table to hold data
CREATE TABLE #Cars (id int)

--- Add a number of Rows to table
SET @x = 1
WHILE(@x < 10000)
    INSERT INTO #Cars Select round((rand()*100),0)
    SET @x = @x + 1

--- Delete all the rows in chunks of 5000
--- If the number of ROWS processed in the DELETE statement are not Zero 
--the repeat the delete statement

    DELETE TOP(5000) FROM #Cars
if @@RowCount != 0
goto DeleteThem   

Friday, January 6, 2012

SQL Server - Altering tables and renaming columns

 A quick post on how to alter the data types and nullable attributes for a table.

In addition, since you would think that the same command statement would also take care of renaming a column I've added that as well.

First we create a test table to work with, as usual I'll stick with cars.

 After the table has been created, we realized that the Make is only five characters.  That will need to be fixed.

For some reason, it was decided that the Year can not be nullable.  They don't care about the Make or Model, go figure.

Then finally, we are told that Year really shouldn't be used.  They want us to use ModelYear instead.  But wait, ALTER TABLE just doesn't allow column name changes.  So we must use the system stored procedure SP_RENAME.

Below we'll be using SP_RENAME to rename the column.  But it can also be used to rename databases, indexes, objects and user data types.  See: msdn:SP_RENAME for more information.

-- Below creates a sample table called cars:

--- Create a Table ---
    ID     INT          Identity(1,1) NOT NULL
  , Year   INT         NULL
  , Make   VarChar(05) NULL
  , Model  VarChar(50) NULL


-- the Alter TABLE statement allows you to modify the
-- data type and the nullable attribute of a column.

-- Here we are increasing the size of the Make
-- column to 50 characters from the initially created 05
    ALTER COLUMN Make Varchar(50) NULL

-- Let's prevent null values from being entered
-- into the Year column. 
--Note: If there are already null values in the
--Year column, this command would fail.


-- There is no ALTER command to rename a column
-- for this you will need to use 'sp_rename'
EXEC sp_rename 'dbo.Cars.Year', 'ModelYear', 'column'

--Note: You will receive a caution message indicating that
--      your change could break any existing scripts or
--      stored procedures.  So make sure you update any
--      affected stored procedures or scripts.