Question

如何通过'a'生成字符串'zzz'，然后使用MySQL将它们保存到表中？

Answer 1

这有点难以从“纯”MySQL中做到，原因有两个：

不支持递归查询，强制您使用临时表生成所有可能的variations。
但是，临时表can't be referenced multiple times from the same query，因此您无法在其上使用笛卡尔积（即CROSS JOIN）来生成变体。这会强制您使用“真实”表而不是临时表。

鉴于这一切，解决方案将如下所示：

CREATE TABLE TEMP_CHARS (
    C CHAR PRIMARY KEY
);

INSERT INTO TEMP_CHARS VALUES('a'), ('b'), ('c'), ('d'), ('e'), ('f'), ('g'), ('h'), ('i'), ('j'), ('k'), ('l'), ('m'), ('n'), ('o'), ('p'), ('q'), ('r'), ('s'), ('t'), ('u'), ('v'), ('w'), ('x'), ('y'), ('z');

INSERT INTO YOUR_TABLE(YOUR_FIELD)
SELECT C
FROM TEMP_CHARS
UNION ALL
SELECT CONCAT(T1.C, T2.C) -- Generate all variations (with repetition) of length 2.
FROM TEMP_CHARS T1 CROSS JOIN TEMP_CHARS T2
UNION ALL
SELECT CONCAT(T1.C, T2.C, T3.C) -- Generate all variations (with repetition) of length 3.
FROM TEMP_CHARS T1 CROSS JOIN TEMP_CHARS T2 CROSS JOIN TEMP_CHARS T3;

DROP TABLE TEMP_CHARS;

Answer 2

如果你知道join = cartesian product，那就很容易了以下（使用用户定义函数@Branko Dimitrijevic的替代版本），
你可以放入一个文本文件（join.sql）： -

create table abc ( a char(3) );
create table a ( a char(1) );
insert into a values ('a','b' ..., 'z');

insert into abc select a from a;

insert into abc
select concat(a.a, b.a) from a
join a as b;

insert into abc
select concat(a.a, b.a, c.a) from a
join a as b
join a as c;

管道进入mysql

mysql -u xxx -h xxx < join.sql

如何生成字符串'a'..'zzz'然后将它们保存到表中？

2 个答案: