SELECT u.username, vs.* FROM users u CROSS JOIN vscode_extensions vs USING (uid);

$users = @(
    [PSCustomObject]@{ uid = 1001; username = 'Alice' },
    [PSCustomObject]@{ uid = 1002; username = 'Bob' }
)

$vscode_extensions = @(
    [PSCustomObject]@{ uid = 1001; extension = 'ms-python.python'; version = '2023.10.0' },
    [PSCustomObject]@{ uid = 1002; extension = 'ms-vscode.cpptools'; version = '1.15.0' },
    [PSCustomObject]@{ uid = 1001; extension = 'ms-vscode.PowerShell'; version = '2023.9.0' }
)

$result = foreach ($user in $users) {
    foreach ($ext in $vscode_extensions | Where-Object { $_.uid -eq $user.uid }) {
        [PSCustomObject]@{
            username  = $user.username
            uid       = $user.uid
            extension = $ext.extension
            version   = $ext.version
        }
    }
}

$result | Format-Table -AutoSize