mysql - SQL | insert into + select + variables with condition? -

my task inserting 3 random datas per id table
, got mistake syntax

set @num := 0, @type := '' ,@stat :=''; insert random   ( select * ( select userid,username, chaid, chaname,goal,gender,       @num := if(@type = userid, @num +1,1) row_number,       @type := userid dummy,       @stat status   userchar   order userid ) x x.row_number <= 3) 

i'm going put code in event scheduler insert new datas in daily

1064 - have error in sql syntax; check manual corresponds mariadb server version right syntax use near 'insert random ( select * ( select userid,username, chaid, c' @ line 2

thank every suggestions.

i suspect problem trying run multiple statements @ same time. can fix initializing variables in query itself:

insert random( . . . )     select u.*     (select userid, username, chaid, chaname, goal, gender,                  (@num := if(@u = userid, @num +1,                             if(@u := userid, 1, 1)                            )                 ) row_number,                 userid dummy,                 @stat status            userchar u cross join                 (select @u = '', @num := 0, @stat := '') params            order userid, rand()           ) u     u.row_number <= 3; 

there several other issues:

• when using insert, list columns. particularly important if learning sql, learn habits.
• you should not assign variable value in 1 expression , use in another. mysql (and mariadb) not guarantee order of evaluation of expressions in select, expressions can evaluated in either order.
• if want random rows, use rand(). there difference between "indeterminate" , "random".