Question

请注意，我正在为我的主查询和子查询调用并加入相同的表。

现在我的实际查询正在使用更多这样的子查询。

有没有办法从主查询中调用子查询字段，从而无需在子查询中重用相同的连接表？我想在不牺牲速度的情况下提高效率。

SELECT tb1.id, tb1.title,

(SELECT tb1.title 
FROM table1 AS tb1
JOIN table2 AS tb2 ON tb2.id = tb1.id 
LEFT JOIN table3 AS tb3 ON tb2.id = tb3.id 
WHERE tb1.id > '123' LIMIT 1) AS next

FROM table1 AS tb1
JOIN table2 AS tb2 ON tb2.id = tb1.id 
LEFT JOIN table3 AS tb3 ON tb2.id = tb3.id
WHERE tb1.id='123'

Answer 1

您可以使用View来抽象该查询。

CREATE VIEW tbl_view AS 
SELECT 
tb1.id as id,
tb1.title as title  
FROM table1 AS tb1
JOIN table2 AS tb2 ON tb2.id = tb1.id 
LEFT JOIN table3 AS tb3 ON tb2.id = tb3.id

较短的查询将是

SELECT 
  id, 
  title,
  (SELECT title FROM tbl_view
  WHERE id > '123' LIMIT 1) AS next
FROM 
  tbl_view
WHERE id='123'

有没有办法绕过子查询中的重复表？

1 个答案: