SA0110 : Avoid have stored procedure that contains IF statements

Introduction

Avoid using conditional logic in stored procedures, functions, and triggers to prevent optimizer confusion and parameter sniffing issues.

Description

Conditional logic in SQL Server stored procedures, functions, and triggers can lead to issues with the SQL query optimizer. This problem arises because the presence of IF or IF..ELSE statements can obscure the optimal execution plan selection, which may result in inefficient query performance.

For example:

-- Example of problematic use of conditional logic within a stored procedure
CREATE PROCEDURE SampleProcedure
AS
BEGIN
    IF (@SomeCondition = 1)
    BEGIN
        SELECT * FROM TableA;
    END
    ELSE
    BEGIN
        SELECT * FROM TableB;
    END
END

This example illustrates how conditional logic can lead to inconsistent execution plans being chosen during runtime, impacting performance. The SQL Server optimizer may not be able to accurately determine the best execution path, especially if parameters vary during calls.

Leads to performance problems due to suboptimal execution plans.
Causes parameter sniffing issues where cached plans may not suit all execution scenarios.

How to fix

Refactor stored procedures to minimize the use of conditional logic, enhancing performance by ensuring optimal execution plans and reducing parameter sniffing issues.

Follow these steps to address the issue:

1.Identify portions of the stored procedure that contain conditional logic, especially those using IF or IF..ELSE statements.

2.Separate the conditional logic into distinct stored procedures. Each branch of the condition should be placed in its own stored procedure tailored to handle specific logic.

3.In the “main” stored procedure, replace the conditional blocks with calls to these new stored procedures based on condition evaluation.

For example:

-- Original procedure with conditional logic
-- CREATE PROCEDURE SampleProcedure
-- AS
-- BEGIN
--     IF (@SomeCondition = 1)
--     BEGIN
--         SELECT * FROM TableA;
--     END
--     ELSE
--     BEGIN
--         SELECT * FROM TableB;
--     END
-- END

-- Refactored approach
CREATE PROCEDURE SampleProcedure
AS
BEGIN
    IF (@SomeCondition = 1)
    BEGIN
        EXEC SpecificProcedureForCondition1;
    END
    ELSE
    BEGIN
        EXEC SpecificProcedureForCondition2;
    END
END;

CREATE PROCEDURE SpecificProcedureForCondition1
AS
BEGIN
    SELECT * FROM TableA;
END;

CREATE PROCEDURE SpecificProcedureForCondition2
AS
BEGIN
    SELECT * FROM TableB;
END;

Scope

The rule has a Batch scope and is applied only on the SQL script.

Parameters

Name	Description	Default Value
IgnoreIfStatementsWhichDoNotContainDmlOrDddlStaetmetns	Ignore IF statements which do not contain any DML or DDL statement.	yes

Remarks

The rule does not need Analysis Context or SQL Connection.

Effort To Fix

1 hour per issue.

Additional Information

There is no additional info for this rule.

Example Test SQL

CREATE PROCEDURE testsp_SA0110
(
  @Code VARCHAR(30) = NULL
)
AS

IF @Code IS NULL
  SELECT * FROM Table1
ELSE
  SELECT * FROM Table1 WHERE Code like @Code + '%'

Analysis Results

	Message	Line	Column
1	SA0110 : Avoid have stored procedure that contains IF statements.	7	0

Analysis Rules