SQL Server 2022

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select json_value(N'{"1ab":123}', N'$.1ab');
Msg 13607 Level 16 State 4 Line 1
JSON path is not properly formatted. Unexpected character '1' is found at position 2.

select json_value(N'{"普":123}', '$."普"');

(No column name)

null

select json_value(N'{"普":123}', N'$."普"');

(No column name)

123