What is the difference between Collation UNICODE_CI_AI, UNICODE_CI and UNICODE

Question

There is a difference between UNICODE_CI_AI, UNICODE_CI and UNICODE? What they are and what they interfere with in the database?

Answer 1

Collation (Collation) nothing more than the character encoding existing in the Database.
There are settings for character sets and Collations (collations) on four levels:

1. Server.
2. Database.
3. Table.
4. Connection.

When you migrate content from a database, sometimes there may be conflicts in the collation of the migrated database. The result of this conflict is the absence of special characters when information is consulted in the database.

You registered the word "Joseph" in your database, but when the programming of your site or system searches this item, returns the result "Jos?". That is, accentuated characters such as (is, ã, õ, etc.) are replaced by the sign "?" (query) or other characters. Source: https://uolhost.uol.com.br/faq/v2/banco-de-dados/o-que-e-collation-de-uma-base-de-dados-como-alterar.html#rmcl

• UTF-8
  It is a variable-width character encoding capable of encoding all 1,112,064 valid code points in Unicode using from one to four 8-bit bytes. Coding is defined by default Unicode and was originally designed by Ken Thompson and Rob Pike. The name is derived from the Transformation Format Unicode or (Universal Coded Character Set) - 8 bits.

• Collation*
  Each character set has a standard intercalation sequence (COLLATE) that specifies the order of grouping. It usually provides nothing more than sorting based on the numeric character code and a basic mapping of upper and lower case characters. If any behavior is required for sequences that are not provided by the standard intercalation sequence and an adequate alternative collation is supported for that character set, a clause COLLATE collation may be specified in the definition of the column.
  
  A clause COLLATE collation can be applied in contexts other than the column definition. For comparison operations greater than/less than, it can be added in clause WHERE of an instruction SELECT. If the output needs to be classified in a special alphabetical sequence, or without distinction between capital letters and lowercase, and the appropriate glue exists, a clause COLLATE may be included with the clause ORDER BY when lines are being classified into a character field and with the clause GROUP BY in the case of group operations.
  

Collation for Character Set UTF8: