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POGet undefined join values
primarykey
Id
15712538
data
AcceptedAnswerId
0
AnswerCount
2
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-03-29T22:43:21.017
FavoriteCount
0
LastActivityDate
2013-03-30T00:12:06.067
LastEditDate
2013-03-30T00:12:06.067
LastEditorUserId
1166877
OwnerUserId
1166877
ParentId
0
PostTypeId
1
Score
0
ViewCount
44
LastEditorDisplayName
text
Body
I have 3 tables: a shop table, a stock table, and a stock_amounts table. The shop table defines each shop's details, the stock tables defines all stock items, and the stock_amounts table defines how much stock each shop has of an item. My tables look like this: <pre><code>*Shop table: | id | shop ------------- | 1 | Head Office | 2 | shop 1 *Stock table: | id | stock_description ------------------------ | 1 | Some description | 2 | Some description | 3 | Some description *Stock amounts table: | id | shop_id | stock_id | stock_amount ------------------------------------------ | 1 | 1 | 1 | 5 | 2 | 2 | 2 | 4 </code></pre> I want to display all the stock that a shop has, but also display the stock that hasn't been defined for that shop. For example, shop 1 has 5 of stock 1, but none of stock 2 or stock 3. I want stock 2 and 3 to display as either zero or NULL value. I'm currently joining it all together. If I do not specify anything in the <code>WHERE</code> clause, all shops with their stock is shown, and NULL is shown for undefined values. If I do <code>WHERE stock_amounts.id <> '2'</code>, then all NULL values no longer show. What I want to know: 1) Why does NULL no longer show if I specify 'not 2' in the WHERE clause? 2) What is the proper way of doing this, and what would the right MySQL query look like? <h2>Edit:</h2> To be clear, I have no problem whatsoever getting which shop has which stock. The problem I'm having is showing all the stock that shop 1 has + all the stock shop 1 does not have. My query: <code>SELECT shop, stock.id stock_id, description, amount</code> <code>FROM stock</code> <code>LEFT JOIN shop_stock ON shop_stock.stock_id = stock.id</code> This query returns: <pre><code>|shop|stock_id|description |amount -------------------------------------- |1 |1 |Some description|5 |2 |2 |Some description|4 |NULL|3 |Some description|NULL </code></pre> If I add <code>WHERE shop <> '2'</code>, the NULL also disappears. I want a query that will return the following table for shop 1: <pre><code>|shop|stock_id|description |amount -------------------------------------- |1 |1 |Some description|5 |NULL|2 |Some description|NULL |NULL|3 |Some description|NULL </code></pre>
Tags
<php><mysql>
Title
Get undefined join values
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USaggregate1166877
UserOwnerUserId
1. USaggregate1166877
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
2. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. This table or related slice is empty.
CommentsPostId
1. This table or related slice is empty.

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