通过带有变量且存在的mysql select语句进行迭代

Question

I have a bit of code where I am setting a variable based on a select statement, and then want to change the parameter so that the all the rows affected in the select statement create one long string in the variable.

In other words, something like this:

set @crstype1 = ''; select t1.col2 from t1 inner join t2 on t1.col1 = t2.col1 where t2.id = 1;

//select stmt provides several rows affected. now I want to make all the rows in one long comma separated string

while exists [select statement] do set @crstype1 = @crstype1 + ',' end while;

I know my syntax is all messed up. Any ideas on how to do this? I'm thinking maybe a for...each would be better?

Thanks.

Answer 1

Use the GROUP_CONCAT() function in MYSQL for this.

Something like:

SELECT GROUP_CONCAT(col1)
FROM tbl1