在MYSQL PHP中获取与GROUP_CONCAT相关的数据

Question

Table 1

Table 2

This is the result for Those Two table i got By using this query:

SELECT t1.*, GROUP_CONCAT(t2.content_id) 
FROM news_categories t1 
LEFT JOIN news_content t2 
    ON t2.cat_ids = t1.cat_id 
GROUP BY t1.cat_id

Result generated

How can I get the information in table2 from the result(table) GROUP_CONCAT(t2.content_id) related to the content_id ?

and Retrive those data from table2 Using PHP

Answer 1

Well, you got a one-to-many relationship here. Meaning one row in table1 can be related to 0-n rows in table2.

If you you group by the primary key of table1 you limit the result to one result row for each row in table one, by using GROUP_CONCAT(table2_col) you concatenate all matching rows of the table2_column with a separator which is comma by default.

Play with the following queries:

SELECT
     t1.*, 
     GROUP_CONCAT(t2.content_id) AS content_ids,
     GROUP_CONCAT(t2.title) AS content_titles
FROM 
    news_categories t1 
        LEFT JOIN news_content t2 ON t2.cat_ids = t1.cat_id 
GROUP BY t1.cat_id

Or

SELECT
     t1.*, 
     t2.*
FROM 
    news_categories t1 
        LEFT JOIN news_content t2 ON t2.cat_ids = t1.cat_id 

I recommend to write out the columns you want, instead of using .*

EDIT

To separate the concatenated values in php have a look at explode

You fetch the data as usual eg

$result = mysqli_query( $query );
while ( $row = mysqli_fetch_assoc( $result ) ) {
    print_r( $row );
}

Have a look at this examples