How to Check for Column Existence in MySQL?

Checking for Column Existence in MySQL Tables

Verifying the existence of a column in a MySQL table is crucial for database management and data operations. However, unlike enterprise-class databases, MySQL requires a specific approach for this task.

Consider the following query:

IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS 
           WHERE TABLE_NAME='prefix_topic' AND column_name='topic_last_update') 
BEGIN 
ALTER TABLE `prefix_topic` ADD `topic_last_update` DATETIME NOT NULL;
UPDATE `prefix_topic` SET `topic_last_update` = `topic_date_add`;
END;

While intuitive, this query fails in MySQL. To solve this issue, a more straightforward approach is recommended:

SHOW COLUMNS FROM `table` LIKE 'fieldname';

PHP Implementation

Using PHP, you can execute the query as follows:

$result = mysql_query("SHOW COLUMNS FROM `table` LIKE 'fieldname'");
$exists = (mysql_num_rows($result))?TRUE:FALSE;

Explanation

The SHOW COLUMNS command provides information about specific columns in a table. By using the LIKE operator, you can filter the results to include only columns with a matching name. If the query returns at least one row, it indicates that the column exists; otherwise, it doesn't.

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