despadvicehdr

### 1) Overview
 The `despadvicehdr` table serves as the header-level repository for **Dispatch Advice** notes. These documents represent pre-shipment instructions or advice generated before the final invoice is created. It tracks logistics details such as vehicle numbers, transhipment information, transport providers, and associated customer codes.
 
 ### 2) Column dictionary
 
 | Column | Type | Nullable | Meaning | Allowed Values | SQL Usage |
 | :--- | :--- | :--- | :--- | :--- | :--- |
 | **index** | integer | NO | Internal primary key | Auto-incrementing | `PRIMARY KEY` |
 | **compcode** | string | YES | Unique company identifier | e.g., "DAS" | `JOIN` to Company tables |
 | **adviceno** | integer | YES | Unique Dispatch Advice Number | e.g., 0, 1, 2 | Unique document identifier |
 | **advicedate** | datetime | YES | Date the advice was issued | | Filtering by date range |
 | **useradd** | string | YES | ID of user who created the record | e.g., "dispatch", "system" | Audit tracking |
 | **usermod** | string | YES | ID of user who last modified the record | | Audit tracking |
 | **addtime** | string | YES | System timestamp for creation | Format: DD-MM-YYYY HH:MM:SS | Audit tracking |
 | **modtime** | string | YES | System timestamp for last modification | | Audit tracking |
 | **custcode** | string | YES | Unique customer identifier | e.g., "SACPL", "TAL-HYD" | `JOIN` to `cust` |
 | **preparation_time** | string | YES | Time of day the advice was prepared | HH:MM | Operational reporting |
 | **Vehnumber** | string | YES | Registration number of the vehicle | e.g., "HR46D4864" | `JOIN` to `Vehiclemas` |
 | **Transhipment** | string | YES | Details regarding intermediate transfer | e.g., "OM LOGISTICS LTD" | Logistics documentation |
 | **remarks** | string | YES | General header-level notes | | Free text |
 | **tpcode** | string | YES | Transport provider/agency code | e.g., "OMLOG", "SBTC" | `JOIN` to `transptmas` |
 | **vehicle** | string | YES | Mode of transportation | e.g., "BYROAD" | Transport categorization |
 | **ExtraInformation** | string | YES | Supplemental notes or data | | Metadata |
 | **Lock** | string | YES | Transaction lock flag | "N" (No), "Y" (Yes) | Permission logic |
 
 ### 3) Relationships & join map
 
 | Target Table | Join Column(s) | Relationship | Source |
 | :--- | :--- | :--- | :--- |
 | **despadvicedtl** | `adviceno`, `compcode` | **One-to-Many**: One header has multiple line items. | Authority (SCHEMA_MAP/REFERENCE) |
 | **cust** | `custcode`, `compcode` | **Many-to-One**: Links advice to specific customer master data. | Authority (REFERENCE) |
 | **invhdr** | `adviceno`, `compcode` | **One-to-One/Many**: Links advice to the subsequent Invoice. | Authority (REFERENCE) |
 | **transptmas** | `tpcode`, `compcode` | **Many-to-One**: Links to transport agency details. | Likely (SCHEMA_MAP) |
 | **Vehiclemas** | `Vehnumber`, `compcode` | **Many-to-One**: Links registration number to vehicle master. | Likely (SCHEMA_MAP) |
 
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