Mysql random rows from all values of another table -

-

i have table 15,000 rows each having unique id , table b 10,000,000 rows multiple rows each unique id in table a. need check table b each id table , select 1 random row each of matching ids. once query runs end 15,000 random rows table b (each unique table id).

i'd assume intense rand() alone or loop it's got involved select.

looked involves 1 table http://explainextended.com/2009/03/01/selecting-random-rows/

not able adjust need.

what this?

select distinct b.a_id b inner join on a.id = b.id order rand(10000000)

Comments

Post a Comment

Popular posts from this blog

How can I edit my VIM config so that Vim treats ".ejs" files the same as it currently treats my html files? -

-
what put in vim config? how change it? i want .html extension...because html... i think need au bufread,bufnewfile *.ejs setfiletype html au short autocmd docs it's idea put inside test if has("autocmd") au bufread,bufnewfile *.ejs setfiletype html endif to avoid error messages if ever use cut-down version of vim doesn't support feature. finally, if have default filetype rule like: au bufread,bufnewfile * setfiletype text then *.ejs rule must above it.
Read more

Python __call__ special method practical example -

-
i know __call__ method in class triggered when instance of class called. however, have no idea when can use special method, because 1 can create new method , perform same operation done in __call__ method , instead of calling instance, can call method. i appreciate if gives me practical usage of special method. django forms module uses __call__ method nicely implement consistent api form validation. can write own validator form in django function. def custom_validator(value): #your validation logic django has default built-in validators such email validators, url validators etc., broadly fall under umbrella of regex validators. implement these cleanly, django resorts callable classes (instead of functions). implements default regex validation logic in regexvalidator , extends these classes other validations. class regexvalidator(object): def __call__(self, value): # validation logic class urlvalidator(regexvalidator): def __call__(self, valu...
Read more