如果 id 值不存在另一个表，则 SQL 加入

Question

I have to join Several table and tables data are below:

Here is want to show all product with both regular and special price which product_id maybe not be exist in oc_special table if not exist it will show 0.000 price in result.

Here is my what i am trying :

SELECT op.product_id, op.model, op.image, op.price, ops.price as discount_price, opc.category_id, opd.name as product_name, opd.description, ocd.name as cat_name FROM oc_product op INNER JOIN oc_product_to_category opc ON opc.product_id = op.product_id INNER JOIN oc_product_description opd ON opd.product_id = op.product_id INNER JOIN oc_category_description ocd ON ocd.category_id = opc.category_id Inner JOIN oc_product_special ops ON op.product_id = ops.product_id where op.status = 1 GROUP BY op.product_id

Here it only returns rows of items which are exists in oc_special table, but i want is to show all the product from oc_product table which product_id may not be exist in oc_special table.

Answer 1

If the results don't exist on ops table how do you expect to get ops.price ?

Anyway, if your current query is working like you say it is, you can quickly check the EXISTS in the WHERE clause to filter the data.

SELECT op.product_id, op.model, op.image, op.price, ops.price as discount_price, opc.category_id, opd.name as product_name, opd.description, ocd.name as cat_name 
FROM oc_product op 
INNER JOIN oc_product_to_category opc ON opc.product_id = op.product_id 
INNER JOIN oc_product_description opd ON opd.product_id = op.product_id 
INNER JOIN oc_category_description ocd ON ocd.category_id = opc.category_id 
INNER JOIN oc_product_special ops ON op.product_id = ops.product_id 
WHERE NOT EXISTS(SELECT product_id FROM oc_product_special)
AND op.status = 1 
GROUP BY op.product_id