# DbUtil

`DbUtil` provides utility methods for interacting with a database, allowing you to query, insert, update, and delete data.

### Methods

#### `queryValue(dbId: Integer, query: String)`

**Description:** Executes a query on the specified database and returns a single string value. It's used for retrieving specific data from a database.

**Parameters:**

* `dbId` (type: Integer): The identifier of the database to query.
* `query` (type: String): The SQL query to execute.

**Returns:** A string containing the result of the query.

**Example: Get the email address of a user based on their username.**

**Use Case**: Useful for retrieving user contact information from a database.

{% code fullWidth="false" %}

```typescript
var userEmail = DbUtil.queryValue(2, "SELECT email from demo501db.users where 
                                username like '" + STARTED_BY_USERNAME+"'
```

{% endcode %}

***

#### `insert(dbId: Integer, sql: String)`

**Description:** Inserts data into the specified database using an SQL insert statement and returns the number of affected rows. It's used for adding new data records to a database.

**Parameters:**

* `dbId` (type: Integer): The identifier of the database to insert into.
* `sql` (type: String): The SQL insert statement.

**Returns:** An Integer representing the number of rows affected by the insert operation.

**Example: Insert a new product into the products database.**

**Use Case**: Common in e-commerce systems for adding new items to the product catalog.

```javascript
var newProductInsert = "INSERT INTO products (name, price) VALUES ('New Product', 50)";
var insertedRowCount = DbUtil.insert(2, newProductInsert);
```

***

#### `update(dbId: Integer, sql: String)`

**Description:** Updates data in the specified database using an SQL update statement and returns the number of affected rows. It's used for modifying existing data records in a database.

**Parameters:**

* `dbId` (type: Integer): The identifier of the database to update.
* `sql` (type: String): The SQL update statement.

**Returns:** An Integer representing the number of rows affected by the update operation.

**Example: Update the status of an order in the orders database.** 

**Use Case:** Common in order management systems to reflect the order's status changes.

```javascript
var updateOrderStatus = "UPDATE orders SET status = 'Shipped' WHERE order_id = 1005";
var updatedRowCount = DbUtil.update(3, updateOrderStatus);
```

***

#### `delete(dbId: Integer, sql: String)`

**Description:** Deletes data from the specified database using an SQL delete statement and returns the number of affected rows. It's used for removing data records from a database.

**Parameters:**

* `dbId` (type: Integer): The identifier of the database to delete from.
* `sql` (type: String): The SQL delete statement.

**Returns:** An Integer representing the number of rows affected by the delete operation.

**Example: Delete expired tasks from the tasks database.**

**Use Case**: Applicable in task management systems to clean up and remove completed or outdated tasks.

```javascript
var deleteExpiredTasks = "DELETE FROM tasks WHERE status = 'Expired'";
var deletedRowCount = DbUtil.delete(4, deleteExpiredTasks);
```