**Use case**

PostgreSQL is using `ALTER TABLE t ALTER COLUMN c TYPE type` instead of `ALTER TABLE t MODIFY COLUMN c type`.
There is a risk that some people already get used to PostgreSQL syntax.

Let's implement it in ClickHouse.

```
tutorial=# ALTER TABLE hits_100m_obfuscated MODIFY COLUMN UserAgentMinor TEXT
tutorial-# ;
ERROR:  syntax error at or near "MODIFY"
LINE 1: ALTER TABLE hits_100m_obfuscated MODIFY COLUMN UserAgentMino...
                                         ^
tutorial=# ALTER TABLE hits_100m_obfuscated ALTER COLUMN UserAgentMinor TYPE TEXT
;
ALTER TABLE
tutorial=#
```

**Proposed implementation**

Implement it in parser level.
return false;
                command->type = ASTAlterCommand::RENAME_COLUMN;
            }
            else if (s_materialize_column.ignore(pos, expected))
            {
                if (!parser_name.parse(pos, command->column, expected))
                    return false;
                command->type = ASTAlterCommand::MATERIALIZE_COLUMN;
                command->detach = false;
                if (s_in_partition.ignore(pos, expected))
                {
                    if (!parser_partition.parse(pos, command->partition, expected))
                        return false;
                }
            }
            else if (s_drop_partition.ignore(pos, expected))
            {
                if (!parser_partition.parse(pos, command->partition, expected))
                    return false;
                command->type = ASTAlterCommand::DROP_PARTITION;
            }
            else if (s_drop_part.ignore(pos, expected))
            {
                if (!parser_string_literal.parse(pos, command->partition, expected))
                    return false;
                command->type = ASTAlterCommand::DROP_PARTITION;
                command->part = true;
            }
            else if (s_drop_detached_partition.ignore(pos, expected))
            {