Question

我想使用select中的单行生成以下输出。

SELECT max(t1.id)+1 as new_id FROM t1;
-> 101

However I want to do

SELECT s.last_id, sequence(1..100000000) as new_id 
FROM (SELECT max(table1.id)+1 as last_id FROM table1) s;
-> 101,1
-> 101,2
-> 101,3 
......
-> 101,100000000

在postgreSQL中，我可以使用：

SELECT s.last_id, generate_series(1,100000000) 
FROM (SELECT max(table1.id)+1 as last_id FROM table1) s;  -- returns 100,000,000 rows

如何在不使用临时表的情况下在 MySQL 中执行此操作？

Answer 1

略微修改布鲁诺的解决方案

SELECT (SELECT COALESCE(max(id),0)+1 FROM table1), 
        @rownum:=@rownum+1 new_id 
FROM 
(SELECT @rownum:=0) r, 
(SELECT 1 UNION ALL SELECT 2) t1,
(SELECT 1 UNION ALL SELECT 2) t2,
(SELECT 1 UNION ALL SELECT 2) t3,
(SELECT 1 UNION ALL SELECT 2) t4,
(SELECT 1 UNION ALL SELECT 2) t5,
(SELECT 1 UNION ALL SELECT 2) t6,
(SELECT 1 UNION ALL SELECT 2) t7
LIMIT 100

或其他没有变量的版本

SELECT (SELECT Coalesce(MAX(id), 0) + 1
        FROM   table1),
       t1.n * 10 + t2.n + 1 AS new_id
FROM   (SELECT 0 AS n UNION ALL
        SELECT 1      UNION ALL
        SELECT 2      UNION ALL
        SELECT 3      UNION ALL
        SELECT 4      UNION ALL
        SELECT 5      UNION ALL
        SELECT 6      UNION ALL
        SELECT 7      UNION ALL
        SELECT 8      UNION ALL
        SELECT 9) t1,
       (SELECT 0 AS n UNION ALL
        SELECT 1      UNION ALL
        SELECT 2      UNION ALL
        SELECT 3      UNION ALL
        SELECT 4      UNION ALL
        SELECT 5      UNION ALL
        SELECT 6      UNION ALL
        SELECT 7      UNION ALL
        SELECT 8      UNION ALL
        SELECT 9) t2
ORDER  BY new_id

Answer 2

感谢@ harper89，我在这里找到答案：

http://use-the-index-luke.com/blog/2011-07-30/mysql-row-generator#mysql_generator_code

CREATE OR REPLACE VIEW generator_16
AS SELECT 0 n UNION ALL SELECT 1  UNION ALL SELECT 2  UNION ALL 
   SELECT 3   UNION ALL SELECT 4  UNION ALL SELECT 5  UNION ALL
   SELECT 6   UNION ALL SELECT 7  UNION ALL SELECT 8  UNION ALL
   SELECT 9   UNION ALL SELECT 10 UNION ALL SELECT 11 UNION ALL
   SELECT 12  UNION ALL SELECT 13 UNION ALL SELECT 14 UNION ALL 
   SELECT 15;

CREATE OR REPLACE VIEW generator_256
AS SELECT ( ( hi.n << 4 ) | lo.n ) AS n
     FROM generator_16 
     CROSS JOIN generator_16 hi;

CREATE OR REPLACE VIEW generator_4k
AS SELECT ( ( hi.n << 8 ) | lo.n ) AS n
     FROM generator_256 lo
     CROSS JOIN generator_16 hi;

CREATE OR REPLACE VIEW generator_64k
AS SELECT ( ( hi.n << 8 ) | lo.n ) AS n
     FROM generator_256 lo
     CROSS JOIN generator_256 hi;

CREATE OR REPLACE VIEW generator_1m
AS SELECT ( ( hi.n << 16 ) | lo.n ) AS n
     FROM generator_64k lo
     CROSS JOIN generator_16 hi;

现在我可以生成我想要的结果：

SELECT s.last_id, g.n as new_id FROM (SELECT max(table1.id)+1 as last_id FROM table1) s
CROSS JOIN generator_256 g
WHERE G.N BETWEEN 1 AND 100
ORDER BY g.n ASC;

使用LIMIT是一个坏主意，因为最多一百万个行将存储在临时表中。使用where，您不需要临时存储。

Answer 3

MYSql中没有任何内容等于generate_series。在阅读了下面的链接之后，似乎SQL除了MySQL之外都会做。

确认Here

看来你必须采取更复杂的路线，但我没有足够的经验给出答案，那里的链接和答案可能会引导你走向正确的方向。

旁注：

您可以使用LIMIT 100仅返回100行，但似乎您需要稍微不同的内容。

Answer 4

约翰，

您使用此表单：

SELECT max(t1.id)+1, @rownum:=@rownum+1 rownum
FROM (SELECT @rownum:=0) r, t1;

测试这个sql我觉得代码已经解决了。

如何选择一行1亿x

4 个答案: