Can I import tabular data in Qgis, without any information about X and Y only the table? I need to join them after importing them.
Since QGIS 2.6 (at least since mmqgis tools were imported in the main menu) this is done by the menu
Layer > Add layer > Add Delimited Text Layer
Browse to your file in the File name field
Under Geometry Definition, choose "No geometry (attribute only table)"
Relevant section in docs: Importing a delimited text file
You can import a csv file and make a join by attributes with the mmqgis plugin.
Extension > Mmqgis > Attributes join from CSV file