Sql - Union

Data System Architecture


Relational Algebra - Union operator in SQL.

How to

generate dynamically a SQL Union statement

Example in oracle:

  statement || decode(rownum, max(rownum) over (partition by 1),' order by numberOfRows, table_name;',' union all')
  select 'select '''||table_name||''' table_name, count(1) numberOfRows from ' || table_name as statement
  from user_tables
  order by table_name

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Set Theory - Union

Set Theory - Union

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