Writing Select Queries in Cassandra Database

When working with Cassandra database, writing select queries is a crucial part of fetching data efficiently. Here are some tips and best practices for writing select queries in Cassandra:

Basic Select Queries

• SELECT * FROM table_name;: This query fetches all columns for all rows in the table.
• SELECT column1, column2 FROM table_name;: This query fetches specific columns for all rows in the table.

Filtering Data

• SELECT * FROM table_name WHERE column1 = ‘value’;: This query filters data based on a specific column value.
• SELECT * FROM table_name WHERE column1 = ‘value’ AND column2 = ‘value’;: This query filters data based on multiple column values using the AND operator.

Sorting Data

• SELECT * FROM table_name ORDER BY column1 ASC;: This query sorts data in ascending order based on a specific column.
• SELECT * FROM table_name ORDER BY column1 DESC;: This query sorts data in descending order based on a specific column.

Limiting Results

• SELECT * FROM table_name LIMIT 10;: This query limits the number of rows returned to 10.

Clustering Columns

• SELECT * FROM table_name WHERE partition_key = ‘value’ AND clustering_column > ‘value’ ALLOW FILTERING;: This query allows filtering on non-indexed columns, but use it judiciously as it can impact performance.

Using Indexes

• CREATE INDEX index_name ON table_name (column_name);: This query creates an index on a specific column to improve query performance.
• SELECT * FROM table_name WHERE indexed_column = ‘value’;: This query utilizes the index to fetch data efficiently.

These are some of the key points to keep in mind when writing select queries in Cassandra database. By following these best practices, you can optimize query performance and retrieve data effectively.