In Databricks SQL, the LIMIT 1 clause is used to restrict the output of a query to only the first row. This can be helpful for various reasons:

1. Performance Optimization: When you only need a single row of data (e.g., checking if a table is empty, getting the most recent record), using LIMIT 1 can significantly improve query performance as the database engine can stop processing after finding the first result.

2. Sampling: You can use LIMIT 1 to quickly obtain a random sample from a large table.

3. Testing: During development, you might use LIMIT 1 to test your queries on a smaller subset of data before running them on the entire dataset.

Syntax:

The basic syntax is simple:

SELECT column1, column2, ...
FROM table_name
LIMIT 1;

Example:

Let’s say you have a table named employees with columns id, name, and salary. To retrieve the first employee in the table, you would run:

SELECT id, name, salary
FROM employees
LIMIT 1;

This will return a single row containing the ID, name, and salary of the first employee in the table.

Important Considerations:

• Order: If you want the first row based on a specific criterion (e.g., the employee with the highest salary), you should use an ORDER BY clause in conjunction with LIMIT 1.
• Default Limit: Databricks has a default display limit of 1,000 rows. However, this is only for display purposes in the notebook interface. The underlying query will still process all rows. To change this setting, you can modify the spark.databricks.query.displayMaxRows configuration.