For decades absorption spectroscopy has been used to study the chemical pattern and enrichment of the inter-stellar and inter-galactic medium, pushing our knowledge at higher redshifts. It comes immediately clear that Quasars and Gamma-ray bursts are the most promising cosmological sources for these kind of studies. In this picture MgII doublets absorbing systems have a critical role, being often associated with Damped-Lyman alpha system, molecular clouds and/or very dynamic environments as galactic superwinds or star-forming regions. Some authors have found that along the same redshift pathlength there are more strong MgII absorbers (Equivalent Width > 1 A) along GRB line of sights than along the QSOs. In this talk I will show some comparison tests between two samples of GRBs and Quasars based on high resolution UVES datasets. These results show that the two samples if absorbers are consistent with being part of the same populations leaving still open the possibility of an intrinsic origin of the absorbers along the GRB line of sights. I will also present some new results in terms of alpha-enhancement based on weak and strong MgII absorbers, which allowed us to investigate the role of Supernovae type I or II in the chemical enrichment history of the Universe.