Windows default application opens the corresponding suffix name file

win10 operating system, why there are so many default applications specified by file type. The suffix name of the number?

Mar.02,2021

under normal circumstances, just ignore it.

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1bd4011-30ee0.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1bd4011-30ee0.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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