What is the difference between “utf8_unicode_ci” and “utf8_unicode_520_ci”

Question

I recently upgraded WAMPServer and now in phpMyAdmin, I see both collations utf8_unicode_ci and utf8_unicode_520_ci. I was using \"utf8_unicode_ci\

Answer 1

As documented under Collation Names:

Unicode collation names may include a version number to indicate the version of the Unicode Collation Algorithm (UCA) on which the collation is based. UCA-based collations without a version number in the name use the version-4.0.0 UCA weight keys: http://www.unicode.org/Public/UCA/4.0.0/allkeys-4.0.0.txt. A collation name such as utf8_unicode_520_ci is based on UCA 5.2.0 weight keys: http://www.unicode.org/Public/UCA/5.2.0/allkeys.txt.