Question

I am not able to find the solution for my problem. I have 4 tables:

BomModule: This table represents a module in the database.

CREATE TABLE "BOMMODULE"
(
    "MODULEID" NUMBER(10,0) NOT NULL ENABLE,
    "ISROOTMODULE"     NUMBER(1,0) NOT NULL ENABLE,
    "MODULENAME"       VARCHAR2(255 CHAR),
    ...
)

BomItem: This table represents a leaf – or an item in the database.

CREATE TABLE "BOMITEM"
(
    "ITEMID"     NUMBER(10,0) NOT NULL ENABLE,
    ...
)

ModuleConnection: This table maps a module to another parent module. You can define the quantity of submodules that belong to a specific parent module.

CREATE TABLE "MODULECONNECTION"
(
    "ID"       NUMBER(10,0) NOT NULL ENABLE,
    "QUANTITY"   NUMBER(10,0) NOT NULL ENABLE,
    "SUBMODULE_MODULEID"   NUMBER(10,0) NOT NULL ENABLE,
    "PARENTMODULE_MODULEID" NUMBER(10,0) NOT NULL ENABLE,
    ...
)

ItemModuleConnection:
This table maps all leave-items to a module. Furthermore, you can define the quantity of items for one module.

CREATE TABLE "ITEMMODULECONNECTION"
(
    "ID"       NUMBER(10,0) NOT NULL ENABLE,
    "QUANTITY" NUMBER(10,0) NOT NULL ENABLE,
    "ITEMID"   NUMBER(10,0),
    "MODULEID" NUMBER(10,0),
    ...
)

As you can see from the table structure, items and modules are connected to each other and have different quantities. Due to the fact that those connections are very flexible, I am not able to create a SQL statement, that will provide me the total quantity for an item:

select quantity from ...... where itemId = xy;

The SQL statement should check all quantities from the item to the root module and multiply them:

2 x rootmodule (total 2)
-- 1x submodule 1 (total 2)
-- 2x submodule 2 (total 4)
---- 5x item 1 (total 20)
---- 6x item 2 (total 24)

Please help me create this sql statement, much appreciate your answer!

Constraints:

– It has to be a SQL statement (It is used in a Java application)
– Database is Oracle 11g

Answer 1

I was able to solve this problem by using Java, instead of SQL. This is my approach:

/**
 * This recursive functions interates through the whole tree and checks if there are items and modules.
 * As soon as an item is found, it is multiplied with the module amount. The result is saved in a HashMap. 
 * This HashMap is being parsed in the end.
 */
public HashMap<Integer, Integer> updateBom(HashMap<Integer, Integer> bom, BomModule module, int amount, BomHandling bh) {
    if(bom == null) {
        bom = new HashMap<Integer, Integer>();
    }
    // get all items for this parent module
    Collection<ItemModuleConnection> items = bh.getItems(module.getModuleId());
    Iterator<ItemModuleConnection> itemIterator = items.iterator();

    while(itemIterator.hasNext()) {
        ItemModuleConnection con = itemIterator.next();

        int itemQuantity = con.getQuantity() * amount;

        // if bom item already exists in bom list, get it and update quantity
        Integer currentItemQuantity = new Integer(0);
        if(bom.containsKey(new Integer(con.getItem().getItemId()))) {
            currentItemQuantity = bom.get(con.getItem().getItemId());
            bom.remove(bom.get(con.getItem().getItemId()));
        }
        bom.put(con.getItem().getItemId(), currentItemQuantity + itemQuantity);
    }

    // get all modules for this parent module
    Collection<ModuleConnection> modules = bh.getConnections(module.getModuleId());
    Iterator<ModuleConnection> moduleIterator = modules.iterator();

    // set the quantity of the module by multiplying it with the amount
    while(moduleIterator.hasNext()) {
        ModuleConnection moduleCon = moduleIterator.next();
        int moduleQuantity = moduleCon.getQuantity();
        updateBom(bom, moduleCon.getSubModule(), moduleQuantity * amount, bh);
    }
    return bom;
}

Before I print the single Items, I call this updateBom()-function and then retrieve the values from the HashMap:

HashMap<Integer, Integer> bom = updateBom(null, bomModule, 1, bh);
Iterator<Map.Entry<Integer, Integer>> entries = bom.entrySet().iterator();

while (entries.hasNext()) {

    Map.Entry<Integer, Integer> bomEntry = entries.next();
    BomItem item = bh.getBomItem(bomEntry.getKey());
    Integer itemAmount = bomEntry.getValue();

    ...
}