Datastore is a vSphere element that only can be assigned to the ESXi host level. you cannot allocate it for the virtual machine (VM) itself, while the VM files resides on the datastore. So if you have a SSD array of disks and want to use it to increase the performance metrics of SQL server virtual machine, there is a good recommendation to change and put the VM's swap file inside a directory that exists on the SSD datastore. (To change the VM swap file default location, see KB1004082)
In some situations, you may faced that ESXi hosts didn't detect your disk storage as a SSD datastore! Then if you are ensure about your disk's type (is SSD), you can mark it manually (KB2013188). This operation needs host reboot.
However if you are not well-done educated about the VMware vSphere, please don't change them, until you understand them well.
At last I suggest to read about the Raw Device Mapping (RDM) too, if you want to became more aware about the types of disk assigning to the virtual machine.