How SQL Server determines that a field contains uppercase letters _MSSQL

The default in the SQL statement is case-insensitive, so the statement:

SQL code
SELECT * from recenginebizinfo WHERE recenginebizname = ' QQ '
And
SQL code
SELECT * from recenginebizinfo WHERE recenginebizname = ' QQ '

The results found are the same.

The script to see if a field contains uppercase A is:
SQL code
SELECT * from Recenginebizinfo where recenginebizname collate chinese_prc_cs_as_ws like '%a% '
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The script to see if a field contains uppercase letters is:
SQL code
SELECT * from Recenginebizinfo Rebi
WHERE Rebi. Recenginebizname COLLATE Chinese_prc_cs_as
Like '%[abcdefghijklmnopqrstuvwxyz]% '

To see if a field contains two consecutive uppercase letters, the script is:
SQL code
SELECT * from Recengineattributeinfo Reai
WHERE Reai. Zhiling COLLATE Chinese_prc_cs_as
Like '%[abcdefghijklmnopqrstuvwxyz][abcdefghijklmnopqrstuvwxyz]% '

by analogy.