Question

I will try and explain this the best way I can.

I have a SQL query which does 3 inner joins with 3 tables to match two ID’s (i.e I have a ‘Item’ table and a ‘itemType’ table. item.itemTypeID is linked with itemType.id).

In my code, if there is no ItemType associated with an Item, then the item.itemTypeID is set to -1.

However when it comes to this query, there is no such itemType with ID -1, so it doesn’t come back with a record.

I need it to come back with all the records that have an itemType, but also all those records with a itemType as -1, and set the relevant returned elements to NULL.

My SQL query is as follows;

`
SELECT items.id

 , items.code
 , items.description
 , items.expirydate
 , items.batchnumber
 , items.serialnumber
 , items.orderref
 , items.datepurchased
 , items.price
 , items.consigcalloff
 , items.commodity_qty
 , itemtypes.code
 , itemtypes.description
 , locations.code
 , locations.description
 , keepers.code
 , keepers.fname
 , keepers.lname
FROM items inner join itemtypes ON items.type = itemtypes.id inner join keepers ON items.keeper = keepers.id inner join locations ON items.location = locations.id`

Answer 1

You’re going to need an outer join.. This will return all records from the items table, irrespective of whether they have a match in the itemType table or not. When no match exists, the itemType fields will be null..

SELECT items.id
 , items.code
 , items.description
 , items.expirydate
 , items.batchnumber
 , items.serialnumber
 , items.orderref
 , items.datepurchased
 , items.price
 , items.consigcalloff
 , items.commodity_qty
 , itemtypes.code
 , itemtypes.description
 , locations.code
 , locations.description
 , keepers.code
 , keepers.fname
 , keepers.lname
FROM items 
       left outer join join itemtypes ON items.type = itemtypes.id 
       inner join keepers ON items.keeper = keepers.id 
       inner join locations ON items.location = locations.id`