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How to Get the Valid DataTable Row Count Following a SQL Query? RRS feed

  • Question

  • This issue has me stumped.  I am setting a DataTable object to the results a SQL query, however getting the correct value of the number of rows of data proves elusive.  When the SQL query executed returns > 1 row (e.g. 5 rows), the Write-Host statement displays this same value (5).  When the SQL query executed returns exactly 1 row, the Write-Host statement displays the value of 0.  When the SQL query executed returns no rows,  the Write-Host statement displays the value of 0.

    Why is the value of Rows.Count correct when the number of rows >1 and not when there is exactly 1 row? In other words this value appears to be non-deterministic for the case of 0 or 1 rows in the DataTable object.

    I have independently verified the number of rows returned by various SQL queries outsid of the PowerShell script.

    Here is a code snippet:

    function ExecuteSqlQuery {
        $Datatable = New-Object System.Data.DataTable
        $Connection = New-Object System.Data.SQLClient.SQLConnection
        $Connection.ConnectionString = "..."
        $Connection.Open()
        $Command = New-Object System.Data.SQLClient.SQLCommand
        $Command.Connection = "..."
        $Command.CommandText = "..."
        $Reader = $Command.ExecuteReader()
        $Datatable.Load($Reader)
        $Connection.Close()
        return $Datatable
    }

    $resultsDataTable = New-Object System.Data.DataTable
    $resultsDataTable = ExecuteSqlQuery
    Write-Host ("Result set contains: " + $resultsDataTable.Rows.Count + " rows." )



    Thursday, September 28, 2017 5:51 PM

Answers

  • This will eliminate that issue:

    $dt =@(ExecuteSqlQuery 'select * from something')
    $dt.Rows.Count


    \_(ツ)_/



    Monday, November 27, 2017 10:40 PM

All replies

  • Functions must be defined before they are called.  Place the function at the top of the script.


    \_(ツ)_/

    Thursday, September 28, 2017 5:56 PM
  • The function does appear in the correct order in the actual script - it is just shown this way for reference.
    Thursday, September 28, 2017 6:46 PM
  • function ExecuteSqlQuery {
    Param($sql) $Datatable = New-Object System.Data.DataTable $Connection = New-Object System.Data.SQLClient.SQLConnection $Connection.ConnectionString = "..." $Connection.Open() $Command = $Connection.CreateCommand() $Command.CommandText = $sql $Reader = $Command.ExecuteReader() $Datatable.Load($Reader) $Connection.Close() ,$Datatable } $dt = ExecuteSqlQuery 'select * from something' $dt.Rows.Count



    \_(ツ)_/


    • Edited by jrv Thursday, September 28, 2017 7:32 PM
    Thursday, September 28, 2017 7:31 PM
  • I am running into similar issue.

    It appears that when 1 row is returned, it is returned as: System.Data.DataRow

    Where as when multiple rows are returned, it is returned as: System.Object[]

    (Object Array).

    In your case: $resultsDataTable.Count will also work since it is simple array.

    Do look at it using getType()

    So, you can handle it like this:

    if ($resultsDataTable -eq $null) {0}

    elseif ($resultsDataTable.getType().FullName -eq "System.Data.DataRow") {1}

    else {$resultsDataTable.Rows.Count}

    • Edited by hpark21 Monday, November 27, 2017 11:05 PM
    Monday, November 27, 2017 10:30 PM
  • This will eliminate that issue:

    $dt =@(ExecuteSqlQuery 'select * from something')
    $dt.Rows.Count


    \_(ツ)_/



    Monday, November 27, 2017 10:40 PM
  • If you use my above function this is not necessary because a true table object is returned even with only one row in it.  The return causes enumeration which cause a singleton to be returned.  Adding the comma before the $dt forces the return to only enumerate the array and the first null element is ignored in the return pipeline thus returning the second object which is the table.


    \_(ツ)_/

    Monday, November 27, 2017 10:47 PM
  • So I had this same issue, I wanted to get the number of data(MDF&NDF) files and number of log files for tempdb

    I exec 

    I created a connection and query VAR called $QDB

    $Tsql = "TSQL code I wanted to run" 

    $TempDBDS = $Qdb.ExecuteWithResults($Tsql) -Ran the TSQL

    $TempdbData=$TempDBDS.Tables[0] -Extracted the data table from the data set that was return

    I then used the measure-object in the pipe line to give me the count result
    $TempDB_DataFile = [int]($TempdbData | Where-Object {$_."File Type" -eq "Rows"} | Measure-Object).count
    $TempDB_LogFiles = [int]($TempdbData | Where-Object {$_."File Type" -eq "LOG"} | Measure-Object).count

    Hope this is of some use to someone :) There are prob better ways but it work for me.

    • Proposed as answer by Pete LakerMVP Saturday, August 3, 2019 2:13 PM
    • Unproposed as answer by jrv Saturday, August 3, 2019 2:19 PM
    Saturday, August 3, 2019 1:16 PM
  • Posting colorized code iss not allowed in this forum. It is unreadable in many browser which is why we supply a code tool on the edit bar.

    It is easiest to get the row count from any data table by just getting the 'Count"

    $datatable.Rows.Count

    All Net collections have a count property and it is much faster then using "Measure-Object"


    \_(ツ)_/

    Saturday, August 3, 2019 1:40 PM
  • You should also avoid adding comments to extremely old threads. IN many cases changes in PowerShell make the topic and answers obsolete.  New answers to old topics can cause confusion.


    \_(ツ)_/

    Saturday, August 3, 2019 1:42 PM
  • For help for all arriving on this thread the following is the best way to return a table from ANY SQLServer instance. As written it can be executed and will return a DataTable correctly.

    function Get-SQLDatatable{
    [OutputType([System.Data.DataTable])] Param( $Instance = '.', $DataBase = 'master', $Query = 'SELECT * FROM sys.syscolumns' ) $connectionString="Server=$Instance;Database=$DataBase;Integrated Security=True;" Try{ $conn=New-Object System.Data.SqlClient.SqlConnection($connectionString) $conn.Open() $command = $conn.CreateCommand() $command.CommandText=$query $reader=$command.ExecuteReader() $dt=new-object System.Data.DataTable $dt.Load($reader) $conn.Close() return $dt } Catch{ Throw $_ } } $dt = Get-SQLDatatable $dt.Rows.Count $dt = Get-SQLDatatable -DataBase TestDB $dt.Rows.Count # ... etc


    \_(ツ)_/



    • Proposed as answer by Pete LakerMVP Saturday, August 3, 2019 2:11 PM
    • Edited by jrv Saturday, August 3, 2019 2:12 PM
    Saturday, August 3, 2019 1:55 PM
  • That's what is so unique about these forums. A two year old thread, rekindled for the next generation with up to date goodness.

    Great thread <3


    #PEJL
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    Saturday, August 3, 2019 2:12 PM