ST_Transform(g, target_srid)

Transforms a geometry from one spatial reference system (SRS) to
another. The return value is a geometry of the same type as the input
geometry with all coordinates transformed to the target SRID,
target_srid. Transformation support is limited to geographic SRSs,
unless the SRID of the geometry argument is the same as the target SRID
value, in which case the return value is the input geometry for any
valid SRS.

ST_Transform() handles its arguments as described in the introduction
to this section, with these exceptions:

o Geometry arguments that have an SRID value for a geographic SRS do
  not produce an error.

o If the geometry or target SRID argument has an SRID value that refers
  to an undefined spatial reference system (SRS), an ER_SRS_NOT_FOUND
  error occurs.

o If the geometry is in an SRS that ST_Transform() cannot transform
  from, an ER_TRANSFORM_SOURCE_SRS_NOT_SUPPORTED error occurs.

o If the target SRID is in an SRS that ST_Transform() cannot transform
  to, an ER_TRANSFORM_TARGET_SRS_NOT_SUPPORTED error occurs.

o If the geometry is in an SRS that is not WGS 84 and has no TOWGS84
  clause, an ER_TRANSFORM_SOURCE_SRS_MISSING_TOWGS84 error occurs.

o If the target SRID is in an SRS that is not WGS 84 and has no TOWGS84
  clause, an ER_TRANSFORM_TARGET_SRS_MISSING_TOWGS84 error occurs.

ST_SRID(g, target_srid) and ST_Transform(g, target_srid) differ as
follows:

o ST_SRID() changes the geometry SRID value without transforming its
  coordinates.

o ST_Transform() transforms the geometry coordinates in addition to
  changing its SRID value.

URL: https://dev.mysql.com/doc/refman/8.0/en/spatial-operator-functions.html

