SELECT x1 FROM table_1, (SELECT x2 FROM table_2 UNION SELECT x3 FROM table_3 ) derived_table; SELECT x1,y1 FROM table_1, (SELECT * FROM table_2) derived_table(column_1, column_2) WHERE column_2 = 1 ;
SELECT x1 FROM table_1, (SELECT x2 FROM table_2 UNION SELECT x3 FROM table_3 ) derived_table; SELECT x1,y1 FROM table_1, (SELECT * FROM table_2) derived_table(column_1, column_2) WHERE column_2 = 1 ;