Unicode Character Sets are distinguished by their pad attribute and collating weight characteristics. See Collation Pad Attributes, and Character Collating Weights. Collation support for  utf16le  is limited. The only collations available are  utf16le_general_ci  and utf16le_bin . These are similar to  utf16_general_ci  and  utf16_bin . •Unicode Collation Algorithm (UCA) Versions •Collation Pad Attributes •Language-Specific Collations •Character Collating Weights •Miscellaneous Information •_general_ci Versus _unicode_ci Collations Unicode Collation Algorithm (UCA) Versions MySQL implements the  xxx _unicode_ci  collations according to the Unicode Collation Algorithm (UCA) described at http://www.unicode.org/reports/tr10/. The collation uses the version-4.0.0 UCA weight keys: http://www.unicode.org/Public/UCA/4.0.0/allkeys-4.0.0.txt. The  xxx _unicode_ci  collations have only partial support for the Unicode Collation Algorithm. Some characters are not supported, and combining marks are not fully supported. This affects primarily Vietnamese, Yoruba, and some smaller languages such as Navajo. A combined character is considered different from the same character written with a single unicode character in string comparisons, and the two characters are considered to have a different length (for example, as returned by the  CHAR_LENGTH()  function or in result set metadata). Unicode collations based on UCA versions higher than 4.0.0 include the version in the collation name. Examples: • utf8mb4_unicode_520_ci  is based on UCA 5.2.0 weight keys (http://www.unicode.org/Public/ UCA/5.2.0/allkeys.txt), • utf8mb4_0900_ai_ci  is based on UCA 9.0.0 weight keys (http://www.unicode.org/Public/UCA/9.0.0/ allkeys.txt). The  LOWER()  and  UPPER()  functions perform case folding according to the collation of their argument. A character that has uppercase and lowercase versions only in a Unicode version higher than 4.0.0 is converted by these functions only if the argument collation uses a high enough UCA version. Collation Pad Attributes Collations based on UCA 9.0.0 and higher are faster than collations based on UCA versions prior to 9.0.0. They also have a pad attribute of  NO PAD , in contrast to  PAD SPACE  as used in collations based on UCA versions prior to 9.0.0. For comparison of nonbinary strings,  NO PAD  collations treat spaces at the end of strings like any other character (see Trailing Space Handling in Comparisons). To determine the pad attribute for a collation, use the  INFORMATION_SCHEMA COLLATIONS  table, which has a  PAD_ATTRIBUTE  column. For example: 1971 mysql>  SELECT COLLATION_NAME, PAD_ATTRIBUTE FROM INFORMATION_SCHEMA.COLLATIONS WHERE CHARACTER_SET_NAME = ’utf8mb4’; +----------------------------+---------------+ | COLLATION_NAME | PAD_ATTRIBUTE | +----------------------------+---------------+ | utf8mb4_general_ci | PAD SPACE | | utf8mb4_bin | PAD SPACE |