Introduction:

MySQL is a popular relational database management system that offers various data types, including ENUM and VARCHAR. ENUM allows you to define a list of possible values for a column, while VARCHAR is used for variable-length character strings. In certain situations, you might need to convert an existing ENUM column to VARCHAR in your MySQL database. In this blog, we will explore two methods to achieve this conversion with detailed explanations and sample code for each method. Additionally, we will provide the program output to showcase the successful transformation.

Method 1: Using ALTER TABLE with CAST

Step 1: Create a Sample Table

Let's start by creating a sample table with an ENUM column that we'll later convert to VARCHAR.

CREATE TABLE enum_example (
  id INT AUTO_INCREMENT PRIMARY KEY,
  color ENUM('red', 'green', 'blue', 'yellow')
);

Step 2: Adding a New VARCHAR Column

Next, we will add a new VARCHAR column to the existing table using the ALTER TABLE statement.

ALTER TABLE enum_example
ADD COLUMN color_new VARCHAR(255);

Step 3: Updating the New Column with ENUM Data

Now, we will update the newly added VARCHAR column with data from the ENUM column by casting it as a character using the CAST function.

UPDATE enum_example
SET color_new = CAST(color AS CHAR);

Step 4: Dropping the Old ENUM Column

Finally, we can drop the old ENUM column from the table.

ALTER TABLE enum_example
DROP COLUMN color;

After executing the method, you can verify the successful conversion by running a SELECT query on the table.

SELECT * FROM enum_example;

Output:

Method 2: Using ALTER TABLE with CASE

Step 1: Create a Sample Table

Let's start by creating a sample table with an ENUM column that we'll later convert to VARCHAR.

CREATE TABLE enum_example (
  id INT AUTO_INCREMENT PRIMARY KEY,
  color ENUM('red', 'green', 'blue', 'yellow')
);

Step 2: Adding a New VARCHAR Column

Next, we will add a new VARCHAR column to the existing table using the ALTER TABLE statement.

ALTER TABLE enum_example
ADD COLUMN color_new VARCHAR(255);

Step 3: Updating the New Column with ENUM Data

Using CASE Now, we will update the newly added VARCHAR column with data from the ENUM column using a CASE statement. The CASE statement helps us map each ENUM value to its corresponding VARCHAR equivalent.

UPDATE enum_example
SET color_new = 
    CASE color
        WHEN 'red' THEN 'rouge'
        WHEN 'green' THEN 'vert'
        WHEN 'blue' THEN 'bleu'
        WHEN 'yellow' THEN 'jaune'
        ELSE 'unknown'
    END;

Step 4: Dropping the Old ENUM Column

Finally, we can drop the old ENUM column from the table.

ALTER TABLE enum_example
DROP COLUMN color;

After executing the method, you can verify the successful conversion by running a SELECT query on the table.

SELECT * FROM enum_example;

Output:

Conclusion:

In this blog, we have explored two methods to convert ENUM to VARCHAR in MySQL databases. The first method using the CAST function is simple and straightforward, but it may not be ideal for large databases due to its performance impact during a full table update. The second method using the CASE statement allows for more customized conversions but requires additional code to map ENUM values to their VARCHAR counterparts.