This is the worst specialization I have taken so far on Coursera, and I have taken several, either from universities or private companies.
The first course is fine for someone who already has SQL knowledge and just needs a refresher, but it is still a course with zero depth in the use of SQL in data science. It is just slides, better explanations of SQL can be found on YouTube.
The second course shows an interesting use of SQL, which is not normally covered. But the structure, assessments, assignments and final project are very open and ambiguous. The explanations are superfluous and you can tell that the course was made in a hurry, with no attention to details and with deficiencies in teaching.
Perhaps the third course is the best, as they present a useful technology and platform.
The final project is a total disappointment, as it is not focused on SQL and its use in Data Science activities, the videos are largely a recycling of those seen in previous courses, so that SQL, which is what the specialization is about, you do not learn something new or have the opportunity to apply it as it really applies in Data Science. Better SQL projects are found on YouTube, but these do not give a certificate endorsed by an educational institution such as the University of California, Davis. Sad that the readings in week four are links to other courses, they did not bother to create material or even reference it in a better way.
Zero material is shared.
After this experience I think I will not take any other course or specialization of this University, as well as not recommend it, I finished it just to receive the certificate, but I think it is not worth spending time on it.