cpoduty

### 1) Overview
 The `cpoduty` table stores the breakdown of duties, taxes, and additional charges associated with specific Purchase Orders (PO). It acts as a child table to both the Purchase Order Header (`cpohdr`) and is often linked to specific line items via the serial number (`sno`). This table is critical for calculating the total landing cost of items by itemizing various tax components (like GST, Excise, or Freight) applied to a PO.
 
 ### 2) Column Dictionary
 
 | Column | Type | Nullable | Meaning | Allowed Values | SQL Usage |
 | :--- | :--- | :--- | :--- | :--- | :--- |
 | **compcode** | string | No | Unique identifier for the company/branch. | e.g., "DAS" | Primary Join Key |
 | **pono** | integer | No | Purchase Order Number. | e.g., 115, 2586 | Foreign Key to `cpohdr` |
 | **duty_code** | integer | No | Code representing the specific tax or duty type. | e.g., 8 (GST), 51, 52 | Foreign Key to `cdutymas` |
 | **amount** | number | Yes | Calculated monetary value of the duty/tax. | e.g., 1528.00 | Aggregate Calculation |
 | **sno** | integer | Yes | Serial number used to sequence duties or link to specific PO lines. | e.g., 2, 3, 4 | Join to `cpodtl.sno` |
 | **duty_per** | number | Yes | The percentage rate applied for the specific duty code. | e.g., 10.0, 5.25 | Calculation Input |
 | **index** | integer | No | Internal system row identifier. | | Primary Key |
 
 ### 3) Relationships & Join Map
 
 The `cpoduty` table is a central component of the Purchase Order tax submodule and connects to the following physical tables based on the `SCHEMA_MAP`:
 
 #### Primary Joins
 * **dbo.cpohdr (Header):** Joins on `pono` and `compcode` to retrieve general PO details (Supplier code, PO date).
 * **dbo.cpodtl (Details):** Joins on `pono`, `compcode`, and `sno` to link a specific tax line to a specific item within the PO.
 * **dbo.cdutymas (Master):** Joins on `duty_code` and `compcode` to fetch the descriptive name of the tax (e.g., "IGST", "Freight Charges").
 
 #### Secondary Joins
 * **dbo.appdutymas / dbo.cappdutymas:** Joins on `duty_code` and `compcode` (Likely used for tax applicability logic).
 * **dbo.cpoduty (Self):** Multiple records exist per `pono` (one for each tax component).
 
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