Question

使用PostgreSQL我有两个查询。我想结合两个查询来返回两个用逗号分隔的整数值。

 SELECT * from newlayerya_1 ORDER BY id DESC LIMIT 1 

 SELECT * from newlayerya_1 ORDER BY id ASC LIMIT 1

- 应该返回例如141,23

我尝试了一些我在网上找到的例子，但对此并不高兴。

CREATE FUNCTION test_ret(a integer, b integer) RETURNS RECORD AS $$
DECLARE 
  ret RECORD;
BEGIN
  -- Arbitrary expression to change the first parameter
  --IF LENGTH(a) < LENGTH(b) THEN
     -- SELECT TRUE, a || b, 'a shorter than b' INTO ret;
      SELECT * from newlayerya_1 ORDER BY id DESC LIMIT 1 INTO ret;
 -- ELSE
    --  SELECT FALSE, b || a INTO ret;
      SELECT * from newlayerya_1 ORDER BY id ASC LIMIT 1 INTO ret;
  --END IF;
RETURN ret;
END;$$ LANGUAGE plpgsql;

Answer 1

试试这个

SELECT id from newlayerya_1 ORDER BY id DESC LIMIT 1 
UNION
SELECT id from newlayerya_1 ORDER BY id ASC LIMIT 1

请记住，两个查询的字段数应相同。

Answer 2

SELECT
    (SELECT id from newlayerya_1 ORDER BY id DESC LIMIT 1),
    (SELECT id from newlayerya_1 ORDER BY id  ASC LIMIT 1)

应避免任何反模式，例如将整数转换为字符串。

或者，甚至更简单...

SELECT
    MAX(ID), MIN(ID)
FROM
    newlayera_1

Answer 3

UNION关键字执行此操作;只要两个查询都返回相同的列（您的那些列）。

Answer 4

SELECT row_number() OVER (ORDER BY id ASC) as rnum1, 
       row_number() OVER (ORDER BY id DESC) as rnum2
from newlayerya_1
where STUFF = 'STUFF'
limit 1

Answer 5

SELECT *
FROM yourdatabase
WHERE ID = (SELECT MAX(ID) FROM yourdatabase) or
ID = (SELECT MIN(ID) FROM yourdatabase);

组合2个基本查询以返回一个结果

5 个答案: