  Understanding the preferences of transient types for host galaxies with
certain characteristics is key to studies of transient physics and galaxy
evolution, as well as to transient identification and classification in the
LSST era. Here we describe a value-added database of extragalactic
transients--supernovae, tidal disruption events, gamma-ray bursts, and other
rare events--and their host galaxy properties. Based on reported coordinates,
redshifts, and host galaxies (if known) of events, we cross-identify their host
galaxies or most likely host candidates in various value-added or survey
catalogs, and compile the existing photometric, spectroscopic, and derived
physical properties of host galaxies in these catalogs. This new database
covers photometric measurements from the far-ultraviolet to mid-infrared.
Spectroscopic measurements and derived physical properties are also available
for a smaller subset of hosts. For our 36333 unique events, we have
cross-identified 13753 host galaxies using host names, plus 4480 using host
coordinates. Besides those with known hosts, there are 18100 transients with
newly identified host candidates. This large database will allow explorations
of the connections of transients to their hosts, including a path toward
transient alert filtering and probabilistic classification based on host
properties.
