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Description

This error occurs when attempting to create or alter a MySQL VIEW whose underlying SELECT statement includes a user-defined variable, session variable, or a parameter. MySQL views are designed to represent a fixed, pre-defined query result set, and their definitions do not support dynamic elements like variables or parameters that change per session or invocation.

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Error Message

View's SELECT contains a variable or parameter

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Known Causes

3 known causes

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User-Defined Variables in View

The SELECT statement defining the view includes one or more user-defined variables (e.g., @my_variable), which are not permitted in view definitions.

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Referencing Session Variables

The view's SELECT statement inadvertently references a session-specific system variable (e.g., @@session.time_zone) which MySQL considers a dynamic parameter.

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Attempting Parameterized Views

A misconception that views can accept parameters like stored procedures or functions, leading to an attempt to emulate this behavior with variables.

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Solutions

3 solutions available

1. Remove Variables from View Definition easy

The most direct solution is to eliminate any variables used within the view's SELECT statement.

1

Identify the view causing the error by examining the error message or by reviewing your view definitions.

2

Examine the `SELECT` statement of the problematic view. Look for any usage of user-defined variables (e.g., `@my_variable`) or session variables.

3

Replace the variable with a static value, a column from one of the underlying tables, or a subquery that produces the desired result without using variables.

Example: If your view was `CREATE VIEW my_view AS SELECT @my_var := column1 FROM my_table;`, change it to `CREATE VIEW my_view AS SELECT column1 FROM my_table;` or `CREATE VIEW my_view AS SELECT 123 AS static_value FROM my_table;` if a static value is appropriate.

4

Recreate the view with the modified `SELECT` statement.

DROP VIEW IF EXISTS your_view_name;
CREATE VIEW your_view_name AS
SELECT column1, column2 -- ... modified SELECT statement ...
FROM your_table;

2. Use Stored Procedures for Dynamic Logic medium

For logic that inherently requires variables or parameters, consider using stored procedures instead of views.

1

Determine if the functionality you are trying to achieve with the view truly requires dynamic behavior or parameterization. If so, a stored procedure is a better fit.

2

Create a stored procedure that accepts parameters and performs the desired operations, including using variables.

DELIMITER //
CREATE PROCEDURE get_dynamic_data(IN input_param VARCHAR(255))
BEGIN
  DECLARE my_variable INT;
  SET my_variable = (SELECT COUNT(*) FROM your_table WHERE some_column = input_param);
  SELECT column1, column2, my_variable FROM your_table WHERE some_column = input_param;
END //
DELIMITER ;

3

Call the stored procedure when you need to retrieve the dynamic data.

CALL get_dynamic_data('some_value');

3. Pre-calculate Values in Underlying Tables or Temporary Tables medium

If the variable's value is derived from a calculation that can be pre-computed, store it in the base table or a temporary table.

1

Analyze the variable's purpose. If it's a calculated value that doesn't change frequently, consider adding a new column to the underlying table to store this pre-calculated value.

ALTER TABLE your_table ADD COLUMN precalculated_value INT;

2

Populate the new column with the calculated values. This might involve an `UPDATE` statement.

UPDATE your_table SET precalculated_value = (SELECT some_calculation FROM another_table WHERE ...);

3

Alternatively, if the calculation is dynamic but the result is only needed for a specific query session, create a temporary table to store the pre-calculated values.

CREATE TEMPORARY TABLE temp_calculated_values AS
SELECT column1, (SELECT some_calculation FROM another_table WHERE ...) AS calculated_value
FROM your_table;

4

Modify your view's `SELECT` statement to reference the new column in the base table or the `calculated_value` column in the temporary table.

CREATE VIEW my_view AS
SELECT column1, precalculated_value FROM your_table;

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Related Errors

5 related errors

MySQL Error 1351: View SELECT Contains Variable