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| Source: sargable.com |
What Are Sargable Queries? 🤔
"Sargable" is a term derived from "Search ARGument ABLE." It refers to queries that can effectively utilize indexes, making them faster and more efficient. Non-sargable queries, on the other hand, can't leverage indexes well, leading to slower performance. Understanding how to write sargable queries is crucial for optimizing your SQL queries.
Why Sargable Queries Matter 🏃♂️💨
When your queries are sargable, the database can quickly locate the required rows using indexes, much like a well-organized index in a book to find information. Non-sargable queries force the database to scan the entire table, like reading the entire book to find a single piece of information. Let’s explore this with some examples!
Tip 1: Avoid Using Functions or Calculations on Indexed Columns in the WHERE Clause
When you apply functions or calculations to indexed columns in your
WHERE clause, it prevents the database from using the index,
leading to a full table scan.
Bad Query:
WHERE YEAR(order_date) >= 2023
Why It's Bad: The YEAR function is applied to
order_date, an indexed column, making the query non-sargable.
Good Query:
WHERE order_date >= '2023-01-01'
Why It's Good: Direct comparison is made without applying any function, allowing the database to use the index effectively.
Tip 2: Use Direct Comparisons When Possible
Direct comparisons are straightforward and allow the database to leverage indexes. Avoid wrapping columns in functions or performing calculations.
Bad Query:
WHERE SUBSTRING(DealerName, 1, 4) = 'Ford'
Why It's Bad: The SUBSTRING function is applied
to DealerName, making the query non-sargable.
Good Query:
WHERE DealerName LIKE 'Ford%'
Why It's Good: Direct comparison using
LIKE allows the use of an index on DealerName.
Tip 3: Consider Creating a Computed Column or Function-Based Index
If you must use a function on a column, consider creating a computed column or a function-based index if your database supports them.
Bad Query:
WHERE DATEADD(mm, 30, OrderDate) >= GETDATE()
Why It's Bad: The DATEADD function prevents the
use of an index on OrderDate.
Good Query with Computed Column:
First, create a computed column:
ALTER TABLE Orders ADD ComputedDate AS DATEADD(mm, 30, OrderDate)
Then, use the computed column in your query:
WHERE ComputedDate >= GETDATE()
Why It's Good: The computed column pre-computes the date, making the query sargable.
More Detailed Examples 🌟
Let's break down a few more examples to cement our understanding.
Example 1: Date Comparison
Non-Sargable:
WHERE DATEPART(year, OrderDate) = 2023
Sargable:
WHERE OrderDate >= '2023-01-01' AND OrderDate < '2024-01-01'
Why It's Better: Direct comparison on
OrderDate range allows index utilization.
Example 2: String Manipulation
Non-Sargable:
WHERE LOWER(LastName) = 'smith'
Sargable:
WHERE LastName = 'Smith'
Why It's Better: Direct comparison without a function allows
the use of an index on LastName.
Tips for Writing Sargable Queries
1. Avoid Using Functions or Calculations on Indexed Columns in the WHERE Clause
Functions or calculations on indexed columns prevent index usage.
2. Use Direct Comparisons When Possible
Direct comparisons allow the database to efficiently use indexes.
3. If We Need to Use a Function on a Column, Consider Creating a Computed Column or a Function-Based Index
Pre-compute values or use function-based indexes to maintain sargability.
Conclusion 🎉
Understanding and writing sargable queries is key to optimizing your SQL queries. You can significantly improve query performance by avoiding functions on indexed columns, using direct comparisons, and leveraging computed columns or function-based indexes. So, next time you write a SQL query, think sargable and watch your performance soar! 🚀
Happy querying! 😊
Got any tips or tricks for SQL optimization? Drop them in the comments below! 👇
#Database #SQL #SQLQueries #Optimisation #SQLSargable
