分组并在mysql中计数

Question

I have table like this

table1

   col1             
    ______
    data1
    data2
    data3             
    data4             
    data5             

and table2

data1  
_________
data1,data2
data1
data3,data1
data5
data4,data5,data1
data2

Can I have query that joins both tables with result two column first column content table1.col1 list and column 2 content count of data that content like first column

column1|column2             
_______|_______
data1  | 4
data2  | 2
data3  | 1            
data4  | 1          
data5  | 2

For now I use query inside looping in PHP

$s="select col1 from table1";
foreach($conn->query($s) as $r);) {
echo "select count(*) from table2 where data1 like '%$r[col1]%' "; 
}

If there is any query that can achieve without query inside looping.

btw I use pdo query helper instead mysql_query, i just write a little code by using mysql_query.

Thanks.

Answer 1

First of all is that you shouldn't keep multiple values in single field (table2) when you need it's values in SQL queries.

Anyway, you can utilize FIND_IN_SET() MySQL's function to join both tables and then use GROUP BY and COUNT(*) to get what you need.

SELECT table1.col1 as column1, count(*) as column2
FROM table1
LEFT JOIN tabl2 ON FIND_IN_SET(table1.col1,table2.data1)
GROUP BY table1.col1;

Although there's ready function to do such things, you should keep an eye on performance issues that may occur here.