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The SQL is the most popular API of Apache Flink user that connects so many other engines(i.e. Apache Hive, MySQL, PostgreSQL). Flink would have better compatibility with sql query to the underlying engines it adapters to if it has had the built-in support for implicit type coercion.

There are already some JIRA issues and user mails that are relative with related  this topic more or less.

Use Cases of Type Coercion：

• the inter-operation within builtin SQL operators, like binary arithmetic operations (PLUS, MINOUS and so on), binary comparison, IN, CASE WHEN, IF, SET operator (UNION, INTERSECT ..)
• the built in functions type coercion for input parameters
• the SQL INSERT source that target connector row type when there are are row elements type mismatchmismatches
• the compatibility with other popular DB engines, like MySQL/Hive/PostgreSQL and so on

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