ST_Latitude(p [, new_latitude_val])

With a single argument representing a valid Point object p that has a
geographic spatial reference system (SRS), ST_Latitude() returns the
latitude value of p as a double-precision number.

With the optional second argument representing a valid latitude value,
ST_Latitude() returns a Point object like the first argument with its
latitude equal to the second argument.

ST_Latitude() handles its arguments as described in the introduction to
this section, with the addition that if the Point object is valid but
does not have a geographic SRS, an ER_SRS_NOT_GEOGRAPHIC error occurs.

URL: https://dev.mysql.com/doc/refman/8.0/en/gis-point-property-functions.html

