Unix Server Tech Knowledge Base

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====== Altering Tables ======

===== Adding a column =====

To add a column **if it does not exist** you can do a Prepare/Execute function as follows:
<code sql>
SET @dbname = DATABASE();
SET @tablename = "tableName";
SET @columnname = "colName";
SET @preparedStatement = (SELECT IF(
  (
    SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
    WHERE
      (table_name = @tablename)
      AND (table_schema = @dbname)
      AND (column_name = @columnname)
  ) > 0,
  "SELECT 1",
  CONCAT("ALTER TABLE ", @tablename, " ADD ", @columnname, " INT(11);")
));
PREPARE alterIfNotExists FROM @preparedStatement;
EXECUTE alterIfNotExists;
DEALLOCATE PREPARE alterIfNotExists;
</code>

Other ways of doing this are available in the discussion at [[https://stackoverflow.com/questions/24571611/mysql-alter-table-if-column-not-exists]]

===== Links =====
  * [[https://stackoverflow.com/questions/24571611/mysql-alter-table-if-column-not-exists]]