Functions/GenXdev.Data.SqlServer/Get-SQLServerViewColumnData.ps1

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<#
.SYNOPSIS
Retrieves column data from a SQL view with optional record limiting.

.DESCRIPTION
Executes a SELECT query against a specified SQL view to retrieve data from a
single column. Supports connecting via either a connection string or database file
path. Allows limiting the number of returned records or retrieving all records.

.LICENSE
Copyright (C) 2026 René Vaessen / GenXdev

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.

.PARAMETER ConnectionString
The SQL database connection string. This parameter is mutually exclusive with
DatabaseFilePath.

.PARAMETER DatabaseFilePath
The full path to the SQL database file. This parameter is mutually exclusive
with ConnectionString.

.PARAMETER ViewName
The name of the SQL view to query data from.

.PARAMETER ColumnName
The name of the column within the view to retrieve data from.

.PARAMETER Count
The maximum number of records to return. Use -1 to return all records. Defaults
to 100 if not specified.

.EXAMPLE
Get-SQLServerViewColumnData -DatabaseFilePath "C:\MyDB.sqlite" `
    -ViewName "CustomersView" `
    -ColumnName "Email" `
    -Count 50

.EXAMPLE
Get-SQLServerViewColumnData "C:\MyDB.sqlite" "CustomersView" "Email"
#>

function Get-SQLServerViewColumnData {

    [CmdletBinding(DefaultParameterSetName = 'DatabaseName')]
    param (
        ###############################################################################
        [Parameter(
            Position = 0,
            Mandatory = $true,
            ParameterSetName = 'ConnectionString',
            HelpMessage = 'The connection string to the SQL Server database.'
        )]
        [string]$ConnectionString,
        ###############################################################################
        [Parameter(
            Position = 0,
            Mandatory = $true,
            ParameterSetName = 'DatabaseName',
            HelpMessage = 'The name of the SQL Server database.'
        )]
        [ValidateNotNullOrEmpty()]
        [string]$DatabaseName,
        ###############################################################################
        [Parameter(
            Position = 1,
            ParameterSetName = 'DatabaseName',
            HelpMessage = 'The SQL Server instance name.'
        )]
        [string]$Server = 'localhost',
        ###############################################################################
        [Parameter(
            Position = 2,
            Mandatory = $true,
            HelpMessage = 'The name of the view.'
        )]
        [string]$ViewName,
        ###############################################################################
        [Parameter(
            Position = 3,
            Mandatory = $true,
            HelpMessage = 'The name of the column.'
        )]
        [string]$ColumnName,
        ###############################################################################
        [Parameter(
            Position = 4,
            Mandatory = $false,
            HelpMessage = 'The number of records to return. Default is 100. -1 for all.'
        )]
        [int]$Count = 100
    )

    begin {

        # log the start of the operation
        Microsoft.PowerShell.Utility\Write-Verbose "Starting Get-SQLServerViewColumnData for view '$ViewName'"
    }


    process {

        # determine if we need to limit the results or get all records
        if ($Count -eq -1) {
            # construct query to get all records
            $PSBoundParameters['Queries'] = "SELECT $ColumnName FROM $ViewName"
            Microsoft.PowerShell.Utility\Write-Verbose "Querying all records from view '$ViewName'"
        }
        else {
            # construct query with LIMIT clause
            $PSBoundParameters['Queries'] = "SELECT $ColumnName FROM $ViewName LIMIT $Count"
            Microsoft.PowerShell.Utility\Write-Verbose "Querying $Count records from view '$ViewName'"
        }

        # execute the query using the existing Invoke-SQLServerQuery cmdlet
        GenXdev\Invoke-SQLServerQuery @PSBoundParameters
    }

    end {

        # log completion of the operation
        Microsoft.PowerShell.Utility\Write-Verbose "Completed Get-SQLServerViewColumnData for view '$ViewName'"
    }
}