Idempotent SQL Alter Table Statements

IdempotentSQLAlterTableAddColumn.sql

-- Idempotently add the tasks.id column
SET @table_name = 'tasks';
SET @column_name = 'id';
SET @preparedStatement = (SELECT IF(
  (
    SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
    WHERE table_name = @table_name
      AND column_name = @column_name
      AND data_type = 'BIGINT'
  ) > 0,
  "SELECT 1",
  CONCAT("ALTER TABLE ", @table_name, " ADD COLUMN ", @column_name, " BIGINT(20) COMMENT 'primary key for tasks';")
));
PREPARE alterIfNotExists FROM @preparedStatement;
EXECUTE alterIfNotExists;
DEALLOCATE PREPARE alterIfNotExists;

IdempotentSQLAlterTableRemoveColumn.sql

-- Idempotently remove the tasks.id column
SET @table_name = 'tasks';
SET @column_name = 'id';
SET @preparedStatement = (SELECT IF(
  (
    SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
    WHERE table_name = @table_name
      AND column_name = @column_name
  ) > 0,
  CONCAT("ALTER TABLE ", @table_name, " DROP COLUMN ", @column_name),
  "SELECT 1"
));
PREPARE alterIfNotExists FROM @preparedStatement;
EXECUTE alterIfNotExists;
DEALLOCATE PREPARE alterIfNotExists;