请给我一些帮助。我需要在TIME之前合并两个数据库，但是我不知道如何做。
数据库1（两栖动物）每5秒观察一次。
DATE TIME CDOM Chl LAT LONG
9/13/2019 9:00:01 AM 81.6 16.39 29.908773 -90.272686
9/13/2019 9:00:06 AM 81.56 16.31 29.908773 -90.272686
9/13/2019 9:00:11 AM 81.5 16.19 29.908772 -90.272686
9/13/2019 9:00:16 AM 81.4 16.62 29.908772 -90.272686
9/13/2019 9:00:21 AM 81.45 16.88 29.908772 -90.272686
9/13/2019 9:04:51 AM 81.18 17.37 29.908586 -90.272663
9/13/2019 9:04:56 AM 81.22 17.57 29.90856 -90.272673
9/13/2019 9:05:01 AM 81.25 17.6 29.908522 -90.272668
9/13/2019 9:05:06 AM 81.28 17.66 29.908482 -90.272647
9/13/2019 9:05:11 AM 81.11 17.39 29.908434 -90.272621
9/13/2019 9:05:16 AM 81.13 17.08 29.90838 -90.272595
9/13/2019 9:05:21 AM 80.95 16.99 29.908323 -90.272568
9/13/2019 9:05:26 AM 80.93 17.5 29.908265 -90.27254
9/13/2019 9:05:31 AM 80.81 17.1 29.908209 -90.272523
9/13/2019 9:05:36 AM 80.84 17.29 29.908152 -90.272504
9/13/2019 9:05:41 AM 80.85 17.85 29.908089 -90.272491
9/13/2019 9:05:46 AM 80.84 17.41 29.908029 -90.272485
9/13/2019 9:05:51 AM 80.96 18.21 29.907968 -90.272471
9/13/2019 9:05:56 AM 80.83 17.88 29.907914 -90.272442
数据库2每隔10秒由观察组成。
DATE TIME pCO2
9/13/2019 8:59:57 AM 851.45
9/13/2019 9:00:09 AM 854.42
9/13/2019 9:00:20 AM 856.61
9/13/2019 9:04:56 AM 931.6
9/13/2019 9:05:07 AM 935.23
9/13/2019 9:05:18 AM 940.03
9/13/2019 9:05:29 AM 942.46
9/13/2019 9:05:40 AM 947.5
9/13/2019 9:05:51 AM 949.54
我想合并两个数据库，将pCO2的值与两栖动物中具有相同TIME的列相匹配，但是对于那些不匹配的pCO2 TIMES，我想将它们与两栖动物中的值相匹配。两栖数据库＃1前5秒的范围。
预期结果：
DATE TIME CDOM Chl LAT LONG pCO2
9/13/2019 9:00:01 AM 81.6 16.39 29.908773 -90.272686 NA
9/13/2019 9:00:06 AM 81.56 16.31 29.908773 -90.272686 854.42
9/13/2019 9:00:11 AM 81.5 16.19 29.908772 -90.272686 NA
9/13/2019 9:00:16 AM 81.4 16.62 29.908772 -90.272686 856.61
9/13/2019 9:00:21 AM 81.45 16.88 29.908772 -90.272686 NA
9/13/2019 9:04:51 AM 81.18 17.37 29.908586 -90.272663 NA
9/13/2019 9:04:56 AM 81.22 17.57 29.90856 -90.272673 931.6
9/13/2019 9:05:01 AM 81.25 17.6 29.908522 -90.272668 NA
9/13/2019 9:05:06 AM 81.28 17.66 29.908482 -90.272647 935.23
9/13/2019 9:05:11 AM 81.11 17.39 29.908434 -90.272621 NA
9/13/2019 9:05:16 AM 81.13 17.08 29.90838 -90.272595 940.03
9/13/2019 9:05:21 AM 80.95 16.99 29.908323 -90.272568 NA
9/13/2019 9:05:26 AM 80.93 17.5 29.908265 -90.27254 942.46
9/13/2019 9:05:31 AM 80.81 17.1 29.908209 -90.272523 NA
9/13/2019 9:05:36 AM 80.84 17.29 29.908152 -90.272504 947.5
9/13/2019 9:05:41 AM 80.85 17.85 29.908089 -90.272491 NA
9/13/2019 9:05:46 AM 80.84 17.41 29.908029 -90.272485 NA
9/13/2019 9:05:51 AM 80.96 18.21 29.907968 -90.272471 949.54
9/13/2019 9:05:56 AM 80.83 17.88 29.907914 -90.272442 NA
我能够合并它们，但是我不知道如何合并它们，包括所需的范围/间隔。 在此先感谢！