This example creates one inventoryadjustment with three lines. Note the FQSaveToCache field, set to True except on the last one. Note: You must be in single user mode for this to work.

INSERT INTO "InventoryAdjustmentLine" ("AccountRefListID", "TxnDate", "RefNumber", "Memo", "InventoryAdjustmentLineItemRefListID", "InventoryAdjustmentLineQuantityAdjustmentNewQuantity", "FQSaveToCache") VALUES ('320000-933270542', {d'2003-12-15'}, '1', 'Memo 1', '160000-933272656', 200.0, 1)

INSERT INTO "InventoryAdjustmentLine" ("AccountRefListID", "TxnDate", "RefNumber", "Memo", "InventoryAdjustmentLineItemRefListID", "InventoryAdjustmentLineValueAdjustmentNewValue", "FQSaveToCache") VALUES ('10000-933270541', {d'2003-12-15'}, '1', 'Memo 2', '450000-1071511428', 100.0, 1)

INSERT INTO "InventoryAdjustmentLine" ("AccountRefListID", "TxnDate", "RefNumber", "Memo", "InventoryAdjustmentLineItemRefListID", "InventoryAdjustmentLineQuantityAdjustmentNewQuantity", "FQSaveToCache") VALUES ('10000-933270541', {d'2003-12-15'}, '1', 'Memo 3', '440001-1071511796', 30.0, 0)

Yes, you can adjust the value of a stock item without adjusting the stock quantity. Here is an example:

This item has a COGS Average Cost of $69.73429:

Using QODBC, I adjusted the opening balance equity cost of the stock item by $250.00 using the following SQL insert statement:

INSERT INTO "InventoryAdjustmentLine" ("AccountRefFullName", "TxnDate", "RefNumber", "Memo",
"InventoryAdjustmentLineItemRefFullName", "InventoryAdjustmentLineValueAdjustmentNewValue", "FQSaveToCache")
VALUES ('Opening Bal Equity', {d'2007-05-23'}, '110', 'Value Adj 250', 'Wood Door:Exterior', 250.0, 0)

This item now has a COGS Average Cost of $106.69857:

The value adjustment details can be seen in the Inventory Valuation Detail:

InventoryAdjustmentLine transactions cannot be edited, but to contiune my example, you can adjust the quantity on hand at any point by using the following adjustment example and QuickBooks will automatically do all the value adjustments for you:

INSERT INTO "InventoryAdjustmentLine" ("AccountRefFullName", "TxnDate", "RefNumber", "Memo",
"InventoryAdjustmentLineItemRefFullName", "InventoryAdjustmentLineQuantityAdjustmentNewQuantity", "FQSaveToCache")
VALUES ('Opening Bal Equity', {d'2007-05-23'}, '110', 'Qty Adj 4', 'Wood Door:Exterior', 4, 0)

and the on-hand quantity and average cost is adjusted regardless of the prevous value in the date sequence:

as can be seen here:

But using QODBC you can overhide everything and set the quantity on-hand and the value of the stock to whatever you want. In this example I've reset the quantity on-hand and the asset value by using this insert statement:

INSERT INTO "InventoryAdjustmentLine" ("AccountRefFullName", "TxnDate", "RefNumber", "Memo",
"InventoryAdjustmentLineItemRefFullName", "InventoryAdjustmentLineValueAdjustmentNewQuantity",
"InventoryAdjustmentLineValueAdjustmentNewValue", "FQSaveToCache")
VALUES ('Opening Bal Equity', {d'2007-12-16'}, '110', 'Qty Adj 10 Value 1200',
'Wood Door:Exterior', 10, 1200.0, 0)

which in turn has changed the average cost as $1200.00 / 10 = $120.00:

The value adjustment details can be seen in the Inventory Valuation Detail report:

By the sounds of things I think you are saying that you don't see the change in your ITEM table. The ITEM table is optimized and you need to do:

SELECT * from ITEM verify

to re-optimize the table.