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Tuesday, March 16, 2010

MyEDB SQL One Liner

In this case the use case is to reduce the quantity of each product variation ("ron" in myedb speak), i.e. items in a shopping cart, when the total transaction is finalized. The following code can be placed in a transaction inside a MySQL 5.x stored procedure:


update property natural join int_prop natural join entity_property natural join entity
inner join medb_transaction on entity.eid = medb_transaction.eiddst and entity_property.ron = medb_transaction.ron
and property.prop_group_id = medb_transaction.prop_group_id
set int_val = int_val - qty
where medb_transaction.eidsrc = 8 and property.prop_id = 15

The prop_id 15 is the ID of the 'quantity' property. eidsrc is passed as a parameter to the stored procedure and represents the user id (or "eid" for entity id in myedb speak ;) ).

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