获取由另一个表的字段过滤的每个类别的计数

Question

I have tables with the following structure.

AD_TABLE -

               ID|NAME|CAT_ID|TYPE
               1| car | C0101|Sale
               2|bike | C0201|Want

CAT_TABLE -

              ID   |NAME          |PARENT|LEVEL
              C0100|Vehicle       |C0100 |    0
              C0101|Car           |C0100 |    1
              C0200|Bike/Scooters |C0100 |    1
              C0201|Bike          |C0200 |    2
              C0202|Scooter       |C0200 |    2

I need to get the count of ADs from each category, I have written the following query.

SELECT `CAT_TABLE`.`ID`,`CAT_TABLE`.`NAME`,`CAT_TABLE`.`LEVEL`,`CAT_TABLE`.`PARENT`, COUNT(`AD_TABLE`.`ID`) 
FROM `CAT_TABLE` 
LEFT JOIN `AD_TABLE` ON `AD_TABLE`.`CAT_ID`=`CAT_TABLE`.`ID`
WHERE (`CAT_TABLE`.`ID`='C0100' OR `CAT_TABLE`.`PARENT`='C0100') AND `AD_TABLE`.`TYPE`='0'
GROUP BY `CAT_TABLE`.`ID`

I got the count of each categories properly but after including the AD_TABLE . TYPE`='0' in the where clause categories which do not have ADs were ignored. I need to get all the categories even if the count is 0.

Answer 1

try this

    SELECT     `CAT_TABLE`.`ID`,`CAT_TABLE`.`NAME`,`CAT_TABLE`.`LEVEL`,`CAT_TABLE`.`PARENT`,      COUNT(`AD_TABLE`.`ID`) 
    FROM       `CAT_TABLE` 
    LEFT JOIN  `AD_TABLE` 
    ON         `AD_TABLE`.`CAT_ID`=`CAT_TABLE`.`ID`
    AND        `AD_TABLE`.`TYPE`='0'  -- Write and here..<br/>
    WHERE      (`CAT_TABLE`.`ID`='C0100' OR `CAT_TABLE`.`PARENT`='C0100')
    GROUP BY   `CAT_TABLE`.`ID`