Mysql 更新中的SQL随机值_Mysql_Sql

Mysql 更新中的SQL随机值

mysql sql

Mysql 更新中的SQL随机值,mysql,sql,Mysql,Sql,在MYSQL db中，我需要用一个8到120之间的随机数更新表“people”，但是如果值在103到109之间，我希望它变成110 我将如何进行这样的查询 UPDATE people SET column1 = '________random expression_________' 我还没有测试过，但也许它应该能工作 UPDATE people SET column1 = ( SELECT if(r.rand BETWEEN 103 AND 109, 110, r.rand)

在MYSQL db中，我需要用一个8到120之间的随机数更新表“people”，但是如果值在103到109之间，我希望它变成110

我将如何进行这样的查询

UPDATE people SET column1 = '________random expression_________'

我还没有测试过，但也许它应该能工作

UPDATE people 
SET column1 = (
    SELECT if(r.rand BETWEEN 103 AND 109, 110, r.rand)
    FROM ( SELECT floor(8+rand()*113) rand ) r
)

在代码中生成随机数，并将其传递给数据库。数据库是为处理数据而设计的，并不是实现这一点的理想场所。

我编写了一个Perl脚本，用于运行20000次SQL查询，输出结果表明所选值是正确的（显然，您只是想从脚本中提取并调整SQL以更新表，但我包含了该脚本，以便您可以证明它确实有效）:

#/usr/bin/perl-w
严格使用；
使用DBI；
使用数据：：转储程序；
我的$dbh=DBI->connect（“DBI:mysql:test”、“root”或die$！；
我的$q=execute（）；
my$row=$sth->fetchrow_arrayref（）；
my$int=$row->[0]；
$vals->{$int}++；
}
打印联接（“\n”，排序键%$VAL），“\n”；

我想你可以一直这么做

UPDATE people SET column1 =  floor(8+rand()*113)

UPDATE people 
SET column1 =  110
WHERE column1 BETWEEN 103 AND 109

或者另一种似乎有效但肯定会更好的方法

UPDATE people 
SET column1 = 
(
SELECT rand FROM
(
SELECT 8 as rand UNION ALL
SELECT 9 as rand UNION ALL
SELECT 10 as rand UNION ALL
SELECT 11 as rand UNION ALL
SELECT 12 as rand UNION ALL
SELECT 13 as rand UNION ALL
SELECT 14 as rand UNION ALL
SELECT 15 as rand UNION ALL
SELECT 16 as rand UNION ALL
SELECT 17 as rand UNION ALL
SELECT 18 as rand UNION ALL
SELECT 19 as rand UNION ALL
SELECT 20 as rand UNION ALL
SELECT 21 as rand UNION ALL
SELECT 22 as rand UNION ALL
SELECT 23 as rand UNION ALL
SELECT 24 as rand UNION ALL
SELECT 25 as rand UNION ALL
SELECT 26 as rand UNION ALL
SELECT 27 as rand UNION ALL
SELECT 28 as rand UNION ALL
SELECT 29 as rand UNION ALL
SELECT 30 as rand UNION ALL
SELECT 31 as rand UNION ALL
SELECT 32 as rand UNION ALL
SELECT 33 as rand UNION ALL
SELECT 34 as rand UNION ALL
SELECT 35 as rand UNION ALL
SELECT 36 as rand UNION ALL
SELECT 37 as rand UNION ALL
SELECT 38 as rand UNION ALL
SELECT 39 as rand UNION ALL
SELECT 40 as rand UNION ALL
SELECT 41 as rand UNION ALL
SELECT 42 as rand UNION ALL
SELECT 43 as rand UNION ALL
SELECT 44 as rand UNION ALL
SELECT 45 as rand UNION ALL
SELECT 46 as rand UNION ALL
SELECT 47 as rand UNION ALL
SELECT 48 as rand UNION ALL
SELECT 49 as rand UNION ALL
SELECT 50 as rand UNION ALL
SELECT 51 as rand UNION ALL
SELECT 52 as rand UNION ALL
SELECT 53 as rand UNION ALL
SELECT 54 as rand UNION ALL
SELECT 55 as rand UNION ALL
SELECT 56 as rand UNION ALL
SELECT 57 as rand UNION ALL
SELECT 58 as rand UNION ALL
SELECT 59 as rand UNION ALL
SELECT 60 as rand UNION ALL
SELECT 61 as rand UNION ALL
SELECT 62 as rand UNION ALL
SELECT 63 as rand UNION ALL
SELECT 64 as rand UNION ALL
SELECT 65 as rand UNION ALL
SELECT 66 as rand UNION ALL
SELECT 67 as rand UNION ALL
SELECT 68 as rand UNION ALL
SELECT 69 as rand UNION ALL
SELECT 70 as rand UNION ALL
SELECT 71 as rand UNION ALL
SELECT 72 as rand UNION ALL
SELECT 73 as rand UNION ALL
SELECT 74 as rand UNION ALL
SELECT 75 as rand UNION ALL
SELECT 76 as rand UNION ALL
SELECT 77 as rand UNION ALL
SELECT 78 as rand UNION ALL
SELECT 79 as rand UNION ALL
SELECT 80 as rand UNION ALL
SELECT 81 as rand UNION ALL
SELECT 82 as rand UNION ALL
SELECT 83 as rand UNION ALL
SELECT 84 as rand UNION ALL
SELECT 85 as rand UNION ALL
SELECT 86 as rand UNION ALL
SELECT 87 as rand UNION ALL
SELECT 88 as rand UNION ALL
SELECT 89 as rand UNION ALL
SELECT 90 as rand UNION ALL
SELECT 91 as rand UNION ALL
SELECT 92 as rand UNION ALL
SELECT 93 as rand UNION ALL
SELECT 94 as rand UNION ALL
SELECT 95 as rand UNION ALL
SELECT 96 as rand UNION ALL
SELECT 97 as rand UNION ALL
SELECT 98 as rand UNION ALL
SELECT 99 as rand UNION ALL
SELECT 100 as rand UNION ALL
SELECT 101 as rand UNION ALL
SELECT 102 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 111 as rand UNION ALL
SELECT 112 as rand UNION ALL
SELECT 113 as rand UNION ALL
SELECT 114 as rand UNION ALL
SELECT 115 as rand UNION ALL
SELECT 116 as rand UNION ALL
SELECT 117 as rand UNION ALL
SELECT 118 as rand UNION ALL
SELECT 119 as rand UNION ALL
SELECT 120 as rand

) T
ORDER BY rand()
LIMIT 1
)

谢谢你的帮助，但我真的不明白公式的选择部分（我不知道你在哪里指定最大值120）

floor（8+rand（）*113）

是一个介于8和120之间的随机整数。我刚刚测试了它，我发现了一个问题：它给每一行赋予相同的值，我不想要，我想要每一行different@AdamStrudwick见马丁的评论。但是使用113而不是112，因为

rand（）

的范围是

0，所以我应该首先执行SELECT语句，用PHP生成值，然后对每个被下行投票阻碍的循环执行UPDATE语句。是的，这就是我们所说的“业务逻辑”。只要你想处理“所有数据”，在数据库之外处理可能不好——CPU有SIMD之类的功能，数据库允许一次更新一堆行，原因是：它们可以更好地提高性能，因为它们知道相同的操作（“设置为随机值”）在多个/所有图元上执行，而不是仅在单个图元上执行。所以坚持抽象模型（“数据库只存储数据，不包含业务逻辑”）这并不总是好的—对于存储过程来说，将一些业务逻辑移动到数据库中可能是一件非常有效的事情。如果您开始谈论指令集之类的东西，那么您是在暗示存在大量数据或大量查询。除非这是一个密集的数据处理应用程序，否则我认为您应该从最佳意图/原则开始。“快速简单”并不总是最好的，我只是测试了它，我发现了一个问题：它给每一行赋予了相同的值，我不希望——我希望每一行都不同。你会怎么做这样的查询？通过执行多次更新？因此，您可以对people表中的每个条目反复运行“UPDATE people SET（blah）WHERE person=？”。我想您可以始终执行UPDATE people SET column1=floor（8+rand（）*112）；更新people SET column1=110，其中column1介于103和109之间任何使用第二列的人都应该受到肛门折磨。：）@小偷主人-我不反对！我突然想到，使用用户变量的方法可能有效。。。
UPDATE people 
SET column1 = 
(
SELECT rand FROM
(
SELECT 8 as rand UNION ALL
SELECT 9 as rand UNION ALL
SELECT 10 as rand UNION ALL
SELECT 11 as rand UNION ALL
SELECT 12 as rand UNION ALL
SELECT 13 as rand UNION ALL
SELECT 14 as rand UNION ALL
SELECT 15 as rand UNION ALL
SELECT 16 as rand UNION ALL
SELECT 17 as rand UNION ALL
SELECT 18 as rand UNION ALL
SELECT 19 as rand UNION ALL
SELECT 20 as rand UNION ALL
SELECT 21 as rand UNION ALL
SELECT 22 as rand UNION ALL
SELECT 23 as rand UNION ALL
SELECT 24 as rand UNION ALL
SELECT 25 as rand UNION ALL
SELECT 26 as rand UNION ALL
SELECT 27 as rand UNION ALL
SELECT 28 as rand UNION ALL
SELECT 29 as rand UNION ALL
SELECT 30 as rand UNION ALL
SELECT 31 as rand UNION ALL
SELECT 32 as rand UNION ALL
SELECT 33 as rand UNION ALL
SELECT 34 as rand UNION ALL
SELECT 35 as rand UNION ALL
SELECT 36 as rand UNION ALL
SELECT 37 as rand UNION ALL
SELECT 38 as rand UNION ALL
SELECT 39 as rand UNION ALL
SELECT 40 as rand UNION ALL
SELECT 41 as rand UNION ALL
SELECT 42 as rand UNION ALL
SELECT 43 as rand UNION ALL
SELECT 44 as rand UNION ALL
SELECT 45 as rand UNION ALL
SELECT 46 as rand UNION ALL
SELECT 47 as rand UNION ALL
SELECT 48 as rand UNION ALL
SELECT 49 as rand UNION ALL
SELECT 50 as rand UNION ALL
SELECT 51 as rand UNION ALL
SELECT 52 as rand UNION ALL
SELECT 53 as rand UNION ALL
SELECT 54 as rand UNION ALL
SELECT 55 as rand UNION ALL
SELECT 56 as rand UNION ALL
SELECT 57 as rand UNION ALL
SELECT 58 as rand UNION ALL
SELECT 59 as rand UNION ALL
SELECT 60 as rand UNION ALL
SELECT 61 as rand UNION ALL
SELECT 62 as rand UNION ALL
SELECT 63 as rand UNION ALL
SELECT 64 as rand UNION ALL
SELECT 65 as rand UNION ALL
SELECT 66 as rand UNION ALL
SELECT 67 as rand UNION ALL
SELECT 68 as rand UNION ALL
SELECT 69 as rand UNION ALL
SELECT 70 as rand UNION ALL
SELECT 71 as rand UNION ALL
SELECT 72 as rand UNION ALL
SELECT 73 as rand UNION ALL
SELECT 74 as rand UNION ALL
SELECT 75 as rand UNION ALL
SELECT 76 as rand UNION ALL
SELECT 77 as rand UNION ALL
SELECT 78 as rand UNION ALL
SELECT 79 as rand UNION ALL
SELECT 80 as rand UNION ALL
SELECT 81 as rand UNION ALL
SELECT 82 as rand UNION ALL
SELECT 83 as rand UNION ALL
SELECT 84 as rand UNION ALL
SELECT 85 as rand UNION ALL
SELECT 86 as rand UNION ALL
SELECT 87 as rand UNION ALL
SELECT 88 as rand UNION ALL
SELECT 89 as rand UNION ALL
SELECT 90 as rand UNION ALL
SELECT 91 as rand UNION ALL
SELECT 92 as rand UNION ALL
SELECT 93 as rand UNION ALL
SELECT 94 as rand UNION ALL
SELECT 95 as rand UNION ALL
SELECT 96 as rand UNION ALL
SELECT 97 as rand UNION ALL
SELECT 98 as rand UNION ALL
SELECT 99 as rand UNION ALL
SELECT 100 as rand UNION ALL
SELECT 101 as rand UNION ALL
SELECT 102 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 110 as rand UNION ALL
SELECT 111 as rand UNION ALL
SELECT 112 as rand UNION ALL
SELECT 113 as rand UNION ALL
SELECT 114 as rand UNION ALL
SELECT 115 as rand UNION ALL
SELECT 116 as rand UNION ALL
SELECT 117 as rand UNION ALL
SELECT 118 as rand UNION ALL
SELECT 119 as rand UNION ALL
SELECT 120 as rand

) T
ORDER BY rand()
LIMIT 1
)

update people 
   set `column1` = if ((@a := floor(8+rand()*113)) BETWEEN 103 AND 109 , 110, @a)
       ;