currencyrate

### 1) Overview
 The `currencyrate` table serves as a central repository for foreign exchange rates relative to the Indian Rupee (INR). It allows the system to perform multi-currency conversions for financial reporting and transaction processing, specifically for export-related modules. It maintains rates partitioned by company code (`compcode`) and currency identifier.
 
 ### 2) Column Dictionary
 
 | Column | Type | Nullable | Meaning | Allowed Values | SQL Usage |
 | :--- | :--- | :--- | :--- | :--- | :--- |
 | **index** | integer | NO | Primary key (Internal auto-increment/row index) | | Primary Key |
 | **compcode** | string | NO | Unique identifier for the company/organization branch | e.g., 'DAS', 'PDS' | Join key |
 | **currency** | string | NO | International currency code or symbol | e.g., 'USD', 'a' | Join key |
 | **cname** | string | YES | Formal name of the currency | e.g., 'US Dollar' | Display |
 | **INR** | number | YES | The exchange rate value of 1 unit of foreign currency in Indian Rupees | e.g., 83.50 | Calculation factor |
 
 ### 3) Relationships & Join Map
 
 The `currencyrate` table is primarily joined on a composite key of `compcode` and `currency` to translate foreign transactions into local currency values.
 
 #### Mandatory Joins (SCHEMA_MAP Verified)
 * **dbo.cust**: Linked via `compcode` and `currency`. Used to determine the default exchange rate for specific foreign customers.
 * **dbo.pohdr**: Linked via `compcode` and `currency`. Used in Purchase Orders involving foreign vendors to calculate the estimated local liability.
 * **dbo.exppodtl**: Linked via `compcode` and `currency`. Used to calculate the INR value of export order line items.
 
 #### Likely Joins (Based on REFERENCE_JSON)
 * **dbo.expinvhdr**: (Likely) Though not explicitly defined in the provided schema map, the reference definition uses this join to calculate `itemrate` in INR for stock reporting (`p.currency = s.currency AND p.compcode = s.compcode`).
 
 #### Joins Table
 | Source Table | Join Columns | Logic |
 | :--- | :--- | :--- |
 | `dbo.cust` | `compcode`, `currency` | Retrieves exchange rate for customer profile. |
 | `dbo.pohdr` | `compcode`, `currency` | Converts foreign PO totals to INR. |
 | `dbo.exppodtl` | `compcode`, `currency` | Converts export order item rates to INR. |