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Hi Community,
In this article, we will explore the concepts of Dynamic SQL and Embedded SQL within the context of InterSystems IRIS, provide practical examples, and examine their differences to help you understand how to leverage them in your applications.
InterSystems SQL provides a full set of standard relational features, including the ability to define table schema, execute queries, and define and execute stored procedures. You can execute InterSystems SQL interactively from the Management Portal or programmatically using a SQL shell interface. Embedded SQL enables you to embed SQL statements in your ObjectScript code, while Dynamic SQL enables you to execute dynamic SQL statements from ObjectScript at runtime. While static SQL queries offer predictable performance, dynamic and embedded SQL offer flexibility and integration, respectively.
Dynamic SQL
Dynamic SQL refers to SQL statements that are constructed and executed at runtime, as opposed to static SQL, which is predefined and embedded directly in the application code. Dynamic SQL is particularly useful when the structure of a query is not known in advance or needs to be dynamically adjusted based on user input or application logic.
In InterSystems IRIS, Dynamic SQL is implemented through the %SQL.Statement class, which provides methods for preparing and executing SQL statements dynamically.
Key Benefits of Dynamic SQL
- Flexibility: Dynamic SQL allows you to build queries programmatically, making it ideal for applications with complex or changing requirements.
- Adaptability: You can modify queries based on runtime conditions, such as user input or application state.
- Ad-Hoc Queries: If the application needs to generate custom queries based on user input, Dynamic SQL allows the construction of these queries at runtime.
- Complex Joins and Conditions: In scenarios where the number of joins or conditions can change based on data, Dynamic SQL enables the construction of complex queries.
Practical Examples
1- Dynamic Table Creation: Building Database Schemas on the Fly
This example demonstrates how to dynamically create a table at runtime using InterSystems Dynamic SQL, enabling flexible and adaptive database schema management.
ClassMethod CreateDynamicTable(tableName As %String, columns As %String) As %Status
{
Set sql = "CREATE TABLE " _ tableName _ " (" _ columns _ ")"
Set statement = ##class(%SQL.Statement).%New()
Set status = statement.%Prepare(sql)
If $$$ISERR(status) {
Quit status
}
Set result = statement.%Execute()
If result.%SQLCODE = 0 {
Write "Table created successfully!", !
} Else {
Write "Error: ", result.%SQLCODE, " ", result.%SQLMSG, !
}
Quit $$$OK
}
Invoke Method
USER>do ##class(dc.DESql).CreateDynamicTable("Books","BookID NUMBER NOT NULL,Title VARCHAR(100),Author VARCHAR(300),PublicationYear NUMBER NULL, AvailableFlag BIT")
Output
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