Linkage of two drop-down boxes in AngularJs

two drop-down boxes, for example, the first is a list of provinces and the second is a list of cities. But each first item is "all". How do you write this in AngularJs1.x? The key is this "all", requiring the city to select "all" when the province changes.

Feb.28,2021
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-64f5-1b37958-2c0d3.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b37958-2c0d3.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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