Mysql 8 如何在存储过程中使用 if 和使用 cte

Question

我在存储过程中使用 CTE，它工作正常，但问题是当我尝试添加条件时，我收到以下消息：

You have an error in your sql ..
Syntax to use near 'IF.

CREATE PROCEDURE referrals(LEVEL INT, max_level INT, code VARCHAR(25)) 

WITH RECURSIVE referrals_path (id, NAME, CODE, lvl) AS
 (
SELECT c.id, c.name, c.code, 0 AS lvl
FROM users c
WHERE c.code = code UNION ALL
SELECT c.id, c.name, c.code, cp.lvl + 1
FROM category_path AS cp
JOIN users AS c ON cp.code = c.referred
) 

IF LEVEL > 1 THEN
SELECT * FROM referrals_path; 
ELSE
SELECT * FROM referrals_path WHERE lvl = LEVEL; 

END IF

Answer 1

您不能在查询中使用 IF 语句。它旨在根据条件执行 SQL 代码块，而不是在查询中使用。

不过，我认为您可以按如下方式重新表述您的查询：

WITH RECURSIVE referrals_path (id, NAME, CODE, lvl) AS (
    SELECT c.id, c.name, c.code, 0 AS lvl
    FROM users c
    WHERE c.code = code UNION ALL
    SELECT c.id, c.name, c.code, cp.lvl + 1
    FROM category_path AS cp
    JOIN users AS c ON cp.code = c.referred
) 
SELECT * 
FROM referrals_path
WHERE LEVEL > 1 OR lvl = LEVEL

Mysql 8 如何在存储过程中使用 if 和使用 cte

Mysql 8 How to use an if inside a stored procedure and using cte

mysql

sql

database

recursive-query

where-clause