dec2dms functions are for changing back
and forth between the deprecated Texis/Vortex "degrees minutes
seconds" (DMS) format (west-positive) and "decimal degree" format
for latitude and longitude coordinates. All SQL geographical functions
expect decimal degree parameters (the Vortex
<geo2code> Vortex functions expect Texis/Vortex DMS).
Texis/Vortex DMS values are of the format $DDDMMSS$. For example, 35°15' would be represented as 351500.
In decimal degrees, a degree is a whole digit, and minutes & seconds are represented as fractions of a degree. Therefore, 35°15' would be 35.25 in decimal degrees.
Note that the Texis/Vortex DMS format has west-positive longitudes (unlike ISO 6709 DMS format), and decimal degrees have east-positive longitudes. It is up to the caller to flip the sign of longitudes where needed.