<md-table>
  <ng-container matColumnDef="column1">
    <md-header-cell *matHeaderCellDef>Column 1</md-header-cell>
    <md-cell *matCellDef="let element"> {{element.column1}} </md-cell>
  </ng-container>
  
  <ng-container matColumnDef="column2">
    <md-header-cell *matHeaderCellDef>Column 2</md-header-cell>
    <md-cell *matCellDef="let element"> {{element.column2}} </md-cell>
  </ng-container>
  
  <md-header-row *matHeaderRowDef="displayedColumns"></md-header-row>
  <md-row *matRowDef="let row; columns: displayedColumns;"></md-row>
</md-table>

export class YourComponent {
  displayedColumns: string[] = ['column1', 'column2'];
  
  // 根据条件动态设置需要显示的列
  if (someCondition) {
    this.displayedColumns.push('column3');
  }
}