SQL - Dynamic SQL

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Some programs (a general-purpose report writer for example) must build and process a variety of SQL statements, where the exact text of the statement is unknown until run time. Such statements probably change from execution to execution. They are called dynamic SQL statements.

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Example

SELECT 
  statement||DECODE(ROWNUM, MAX(ROWNUM) over (PARTITION BY 1),' order by aantal, table_name;',' union all')
FROM
(
  SELECT 'select '''||table_name||''' table_name, count(1) numberOfRows from '||table_name AS statement
  FROM user_tables
  ORDER BY table_name
);