What Is Dynamic SQL?

Dynamic SQL enables applications to generate SQL code dynamically based on user inputs or real-time conditions. Unlike static SQL, which is fixed at compile-time, dynamic SQL constructs the query only when it needs to run. This enables more flexible and customizable query behavior across various scenarios.

Examples of Dynamic SQL

A typical example of dynamic SQL involves constructing a query string and running it using sp_executesql. Let’s say we want to view all data from a specific table chosen by the user:

DECLARE @tableName NVARCHAR(MAX), @sql NVARCHAR(MAX);
SET @tableName = 'Customers';
SET @sql = 'SELECT * FROM ' + @tableName;
EXEC sp_executesql @sql;

What this shows: After running the query, the SQL engine executes: SELECT * FROM Customers, dynamically pulling data from the specified table. 

Static SQL vs. Dynamic SQL: Key Differences

Both static and dynamic SQL serve different purposes depending on how flexible or performant the application needs to be.

• Definition: Static SQL is pre-written and compiled before execution. Dynamic SQL is generated on the fly at runtime.
• Flexibility: Dynamic SQL offers adaptability for changing inputs or structures. Static SQL requires code changes for such modifications.
• Performance: Static SQL often delivers better performance due to pre-compiled access paths. Dynamic SQL may need to be parsed and optimized at runtime.
• Execution Planning: Static SQL can use fixed access paths or host variable optimization settings. Dynamic SQL relies on runtime optimization, with options like REOPT(AUTO), REOPT(ONCE), or REOPT(ALWAYS).
• Caching: Static SQL benefits from consistent plans and reuse. Dynamic SQL may use the dynamic statement cache but can incur repeated planning costs.
• Use Case: Choose dynamic SQL when queries need to change frequently, such as generating reports or handling multiple schemas. Use static SQL for well-known, high-performance queries.

Using Dynamic SQL: Step-by-Step Guide

To run dynamic SQL in SQL Server, follow these basic steps:

Step 1: Declare Variables: Define a variable to hold your table name and a second one for the SQL query.

DECLARE @tableName NVARCHAR(MAX), @sql NVARCHAR(MAX);

Step 2: Assign Table Name: Set the value of the table name dynamically.

SET @tableName = N'TargetTable';

Step 3: Construct the SQL Query: Concatenate the SELECT statement with the table name.

SET @sql = N'SELECT * FROM ' + @tableName;

Step 4: Execute the SQL: Use sp_executesql to run the dynamic SQL.

EXEC sp_executesql @sql;

This approach allows dynamic data access based on changing inputs or logic, which is useful in flexible or user-driven applications.

Top Use Cases for Dynamic SQL

Dynamic SQL proves especially useful in situations where query logic must adjust on the fly:

• Interactive reporting: Generate queries with filters, columns, or tables selected by users.
• Multi-client systems: Swap table names or schemas depending on the tenant.
• Dynamic dashboards: Build flexible backends for sorting, searching, or filtering.
• Data orchestration tools: Script conditional operations like MERGE, UPDATE, or DELETE.
• Reusable procedures: Design general-purpose logic adaptable to many input structures.

It’s best suited for cases where fixed SQL simply can’t handle the variability or customization needed in real-time processing.

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Dynamic SQL helps solve problems where flexibility and customization are critical. By enabling dynamic logic in queries, it allows developers and analysts to meet a wide range of business needs without rewriting static code for each scenario. It’s particularly useful in reporting platforms, BI tools, and multi-user data environments.

From Data to Decisions: OWOX BI SQL Copilot for Optimized Queries

OWOX BI SQL Copilot helps you write, validate, and optimize both static and dynamic SQL in BigQuery. With smart suggestions, structure-aware prompts, and context-driven templates, it simplifies query creation across complex logic paths. Whether you're building flexible reports, automating transformations, or personalizing dashboards, SQL Copilot keeps your workflow fast, accurate, and efficient.

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