postgres regular expression - extract magnitude level number from string-CodePudding

I have a column in a postgresql table with strings that contain the magnitude level of an historical list of earthquakes and I need to extract only the number in a separate column. All values have the following pattern:

[Charater "M" or "Md"][space][magnitude level number][" - "][timestamp]

I need to extract only the number but I'm not able to write a specific regular expression to do that, can you help me ? Thanks in advance

 ─────────────────────────────────── ───────────────── 
| Start column                      | Desired output  |
 ─────────────────────────────────── ───────────────── 
| Md 2.7 - 1985-04-18 20:18:02 UTC  | 2.7             |
| M 2.4 - 1985-04-18 17:49:13 UTC   | 2.4             |
 ─────────────────────────────────── ─────────────────

CodePudding user response：

https://regex101.com/r/bMnF3k/1

If think this can work
(?<= )(?:\b\d\.\d\b|\b\d\d\b|\b\d\b)(?= )