After reading @George_Thompson's link, I think a general answer might be ok here. TLDR Just use the same SRID. I don't work out of a database in this manner so this answer is just from principle.
Assumptions:
1. Your underlying coordinate geometry is in the correct SRID. The projection or geographic coordinate system has been defined correctly.
2. You do not need to convert or transform geometry to accomplish your analysis.
3. Edit to add an assumption: All records in the table have the same SRID. Apparently records in a table don't have to share an SRID.
If these assumptions are true and you are changing the geometry type, just use the same SRID. If the feature geometry's coordinate system is unknown or incorrect, you would need to (re)Define it. If you need to use another SRID for an analytic purpose, you would need to Project it.
From the docs:
Unknown coordinate system with an ST_Geometry, SDEBINARY, PostGIS geometry, SDO_Geometry, or SQL Server geometry column
| An SRID greater than 300,000 is added to the geodatabase system table.
|
Definitely wondering what's going on here. What does the XY Coordinate tab say?