SQL Like Operator Syntax and Usage

Note

This feature is only available in NCache Enterprise Edition.

NCache allows you to use the SQL like query format using LIKE Operator in the query to search for a specific pattern in a column.

The two wildcards used with the LIKE operator are:

• *: Used as a substitute for zero or more characters in the string.

• ?: Used as a substitute for a single character in the string.

Pre-Requisites

• .NET/.NET Core
• Java

• 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
  • Alachisoft.NCache.Runtime.Exceptions

• 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 searches the cache and retrieves all the products that have their ProductName starting with the letters Shamp and Category starting with the letters Househo 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 * FROM FQN.Product WHERE ProductName LIKE ? AND Category LIKE ?";

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

  // Providing parameters for query
  queryCommand.Parameters.Add("ProductName", "Cha*");
  queryCommand.Parameters.Add("Category", "Edib*");

  // 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 result = reader.GetValue<string>("ProductID");
      // 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
}

Legacy Syntax

Note

Legacy API is only available in NCache Enterprise Edition.

The following example searches the cache and retrieves all the products that have their ProductName starting with the letters Shamp and Category starting with the letters Househo using ExecuteReader. For Java, the searchEntries method lets you search the cache for keys and objects fulfilling the query criteria.

• .NET/.NET Core
• Java

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.ProductName LIKE ? AND Category LIKE ?";

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

  // Providing parameters for query
  queryCommand.Parameters.Add("ProductName", "Cha*");
  queryCommand.Parameters.Add("Category", "Edib*");

  // 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 Objects
SQL Search for Keys Syntax and Usage
SQL IN Operator Syntax and Usage
SQL GROUP BY Syntax and Usage
Query Operators
Search Cache with LINQ