MS SQL does not come included in any of our legacy VPS packages, either with or without the Plesk control panel. You will have to download this and install it yourself on your Windows VPS if you require it.
The Express Edition of MSSQL is free, however Microsoft charge a licence fee for the Standard Edition.
For more on how to download and install MS SQL express you might find the following knowledgebase article useful:
Please note that some of our newer Virtual Machine\VM templates do come with MSSQL pre-installed. You can see more here: