我可以在不使用过程/函数的情况下在 MySQL 中运行循环吗？
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Can I run a loop in MySQL without using a procedure/function?
提问by Mr. Boy
For testing, is it possible to run a loop from MySQL workbench or similar tool? I tried but got an error.
对于测试，是否可以从 MySQL 工作台或类似工具运行循环？我试过了，但出现错误。
If it is possible, please supply a simple example I can run.
如果可能，请提供一个我可以运行的简单示例。
采纳答案by Thanu
You can't do a for loop in an SQL editor without a stored procedure. I use TOAD for MySQL.
如果没有存储过程，就不能在 SQL 编辑器中执行 for 循环。我将TOAD 用于 MySQL。
A quick stored procedure should do the job:
一个快速的存储过程应该可以完成这项工作：
DELIMITER $$
DROP PROCEDURE IF EXISTS proc_loop_test$$
CREATE PROCEDURE proc_loop_test()
BEGIN
DECLARE int_val INT DEFAULT 0;
test_loop : LOOP
IF (int_val = 10) THEN
LEAVE test_loop;
END IF;
SET int_val = int_val +1;
SELECT int_val;
END LOOP;
END$$
DELIMITER ;
回答by Kache
There's a trick with limited use-cases that is "loop-like".
有一个“类似循环”的有限用例的技巧。
I wanted to create a large (1~2 million) row table of random integers for a test:
我想为测试创建一个大型（1~200 万）随机整数行表：
INSERT INTO test_table (num) VALUES(ROUND(RAND() * 1E6));
-- calling this will insert once for every row in test_table
INSERT INTO test_table (num)
SELECT ROUND(RAND() * 1E6)
FROM test_table;
So I quickly just kept doubling the number of rows until I had what I needed.
所以我很快就把行数加倍，直到我得到我需要的东西。
回答by Volker Raab
Supposed that you already have an arbitrary table myOldTable which is sufficiently long you could use the following trick:
假设您已经有一个足够长的任意表 myOldTable，您可以使用以下技巧：
set @counter = 0;
select (@counter := @counter+1), @counter*@counter from myOldTable limit 1000;
回答by Mike Lischke
If it is that you only want to block the current thread then use select sleep(seconds);otherwise you can use a stored procedure (if there's something you want to loop over) or a UDF (user defined function).
如果您只想阻塞当前线程，则使用select sleep(seconds);其他方式，否则您可以使用存储过程（如果您想要循环遍历）或 UDF（用户定义函数）。
