SQL IN Operator Syntax and Usage

Note

This feature is only available in NCache Enterprise Edition.

In order to search the cache using SQL like query format using IN operator, you can specify multiple attribute values after the IN keyword which means that ExecuteReader will search the cache for all the attributes provided after the IN keyword.

Pre-Requisites

• Indexing for searchable objects and their attributes need to be configured first as explained in Configuring Query Indexes in Administrator's Guide.
• Include the following namespaces in your application:
  • Alachisoft.NCache.Client
  • Alachisoft.NCache.Runtime.Caching
  • Alachisoft.NCache.Client.Services
• The application must be connected to cache before performing the operation.
• Cache must be running.
• Make sure that the data being added is serializable.
• To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Modern Syntax

Here's an example which retrieves Product_Name and UnitsAvailable from the cache having either 10,15,20,25 UnitsAvailable using ExecuteReader

try
{
    // Pre-condition: Cache is already connected
    // Items are already present in the cache

    // Specify the query with the specified criteria
    // Use the Fully Qualified Name (FQN) of your own custom class
    string query = "SELECT ProductName, UnitsAvailable From FQN.Product WHERE UnitsAvailable IN (10,15,20,25)";

    // Use QueryCommand for query execution
    var queryCommand = new QueryCommand(query);

    // Executing QueryCommand through ICacheReader
    ICacheReader reader = cache.SearchService.ExecuteReader(queryCommand);

    // Check if result set is not empty
    if (reader.FieldCount > 0)
    {
      while (reader.Read())
      {
        // Get the value of the result set
        string ProductName = reader.GetValue<string>(1);
        int UnitsAvailable = reader.GetValue<int>(2);

      }
    }
    else
    {
      // Null query result set retrieved
    }
}
catch (OperationFailedException ex)
{
    if (ex.ErrorCode == NCacheErrorCodes.INCORRECT_FORMAT)
    {
        // Make sure that the query format is correct
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
  // Any generic exception like ArgumentException, ArgumentNullException
}

Legacy Syntax

Note

Legacy API is only available in NCache Enterprise Edition.

The following example retrieves all the products from the cache which belong to either Beverages, Produce or Seafood category using ExecuteReader.

try
{
    // Pre-condition: Cache is already connected
    // Items are already present in the cache

    // Specify the query with the specified criteria
    // Use the Fully Qualified Name (FQN) of your own custom class
    string query = "SELECT FQN.Product WHERE this.ProductID IN (1001,1005,2000)";

    // Use QueryCommand for query execution
    var queryCommand = new QueryCommand(query);

    // Executing QueryCommand through ICacheReader
    ICacheReader reader = cache.ExecuteReader(queryCommand);

    // Check if result set is not empty
    if (reader.FieldCount > 0)
    {
      while (reader.Read())
      {
        // Get the value of the result set
        Product result = reader.GetValue<Product>(1);

        // Perform operations
      }
    }
    else
    {
      // Null query result set retrieved
    }
}
catch (OperationFailedException ex)
{
    if (ex.ErrorCode == NCacheErrorCodes.INCORRECT_FORMAT)
    {
        // Make sure that the query format is correct
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentException, ArgumentNullException
}

Recommendation: To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Additional Resources

NCache provides sample application for SQL Searching at:

• GitHub
• Shipped with NCache: %NCHOME%\samples\dotnet\SearchUsingSQL

See Also

Locking Data For Concurrency Control
SQL Search for Keys Syntax and Usage
SQL Search for Keys Syntax and Usage
SQL Like Operator Syntax and Usage
SQL GROUP BY Syntax and Usage
Query Operators
Search Cache with LINQ