如何在SQL数据库中查询许多没有任何通用条件的结果？

SELECT * FROM table1 WHERE condition1
UNION
SELECT * FROM table2 WHERE condition2
UNION
SELECT * FROM table3 WHERE condition3

SELECT * FROM table_name WHERE column_name IN (value1, value2, value3)

SELECT * FROM table_name WHERE condition1 OR condition2 OR condition3

SELECT * FROM table_name WHERE column_name IN (SELECT column_name FROM another_table WHERE condition)

SELECT * FROM table1 JOIN table2 ON table1.column_name = table2.column_name WHERE condition

SELECT * FROM table_name WHERE column_name LIKE '%value%'

SELECT * FROM table_name WHERE column_name BETWEEN value1 AND value2

SELECT COUNT(*) FROM table_name WHERE condition

SELECT DISTINCT column_name FROM table_name WHERE condition

SELECT column_name, COUNT(*) FROM table_name WHERE condition GROUP BY column_name

SELECT * FROM table_name WHERE condition ORDER BY column_name DESC LIMIT 10

SELECT column_name, CASE WHEN condition THEN 'result1' ELSE 'result2' END AS new_column_name FROM table_name

SELECT column_name, (SELECT COUNT(*) FROM another_table WHERE condition) AS subquery_count FROM table_name WHERE condition

CREATE FUNCTION function_name() RETURNS TABLE (column_name1 data_type1, column_name2 data_type2) AS $$
BEGIN
  RETURN QUERY SELECT column_name1, column_name2 FROM table_name WHERE condition;
END;
$$ LANGUAGE plpgsql;

SELECT * FROM function_name();