Mysql：Changes in MySQL 8.0.13 (2018-10-22, General Availability)：utf8mb3 ->utf8mb4

Changes in MySQL 8.0.13 (2018-10-22, General Availability)

Deprecation and Removal Notes

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• InnoDB: Support for TABLESPACE = innodb_file_per_table and TABLESPACE = innodb_temporary clauses with CREATE TEMPORARY TABLE is deprecated and will be removed in a future MySQL version.

• The utf8mb3 character set is deprecated and will be removed in a future MySQL version. Please use utf8mb4 instead.

SQL Syntax Notes

• Incompatible Change: The deprecated ASC or DESC qualifiers for GROUP BY clauses have been removed. Queries that previously relied on GROUP BY sorting may produce results that differ from previous MySQL versions. To produce a given sort order, provide an ORDER BY clause.

  Queries and stored program definitions from MySQL 8.0.12 or lower that use ASC or DESC qualifiers for GROUP BY clauses should be amended. Otherwise, upgrading to MySQL 8.0.13 or higher may fail, as may replicating to MySQL 8.0.13 or higher slave servers.

Functionality Added or Changed

• Important Change: Setting user variables in statements other than SET is now deprecated due to issues that included those listed here:

  • The order of evaluation for expressions involving user variables was undefined.

  • The default result type of a variable is based on its type at the beginning of the statement, which could have unintended effects when a variable holding a value of one type at the beginning of a statement was assigned a new value of a different type in the same statement.

  • HAVING, GROUP BY, and ORDER BY clauses, when referring to a variable that was assigned a value in the select expression list, did not work as expected because the expression was evaluated on the client and so it was possible for stale column values from a previous row to be used.

  Syntax such as SELECT @var, @var:=@var+1 is still accepted in MySQL 8.0 for backward compatibility, but is subject to removal in a future MySQL version.