-6001: Duplicate column name 

Explanation:

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       1.      The column names of a table must differ from each other. Base tables without user-defined key columns and named result tables contain the implicitly created column SYSKEY.

       2.      Named result tables with columns which have not been explicitly named and which do not inherit a column name from the underlying base table implicitly get the column name "EXPRESSION_", where _ stands for a positive integer.

       3.      A column must not be specified more than once in an INSERT or UPDATE statement or in a sequence of key specifications.

User Action:

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       1.      Use different column names.

       2.      In a CREATE VIEW or QUERY statement, uniqueness of column names can be achieved by specifying reference names in the selected columns. In a CREATE VIEW statement, uniqueness can also be obtained by specifying alias names.

       3.      Correct the repeated specification of the same column.