给定一条数据，若数据库中有则更新该数据，没有则新增一条数据。使用merge into实现

1.merge into 的语法 MERGE INTO table_name alias1 USING (table | view | sub_query) alias2 ON (join condition) WHEN MATCHED THEN UPDATE table_name SET col1 = col_val1, col2 = col2_val WHEN NOT MATCHED TH

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