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MySQL: union query fails on MySQL 5.5, works on MySQL 5.1
SELECT information_schema.tables.table_name, schema_tables.db_table, schema_tables.ne_page
  FROM information_schema.tables
  LEFT JOIN (
    (SELECT DISTINCT db_table, ne_page FROM {$db}.nexedit_schema)
    AS schema_tables)
  ON (schema_tables.db_table = information_schema.tables.table_name
    COLLATE utf8_unicode_ci)
  WHERE information_schema.tables.table_schema = '{$db}'
    AND information_schema.tables.table_name NOT LIKE 'nexedit_%'

UNION

SELECT information_schema.tables.table_name, schema_tables.db_table, schema_tables.ne_page
  FROM information_schema.tables
  RIGHT JOIN (
    (SELECT DISTINCT db_table, ne_page FROM {$db}.nexedit_schema)
    AS schema_tables)
  ON (schema_tables.db_table = information_schema.tables.table_name
    COLLATE utf8_unicode_ci)
  WHERE information_schema.tables.table_schema IS NULL
    AND schema_tables.db_table NOT LIKE 'nexedit_%'

GROUP BY information_schema.tables.table_name,schema_tables.db_table;