**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.
break;
        }
        default:
            break;
        case ASTAlterQuery::AlterObjectType::TABLE:
        {
            if (s_add_column.ignore(pos, expected))
            {
                if (s_if_not_exists.ignore(pos, expected))
                    command->if_not_exists = true;
                if (!parser_col_decl.parse(pos, command->col_decl, expected))
                    return false;
                if (s_first.ignore(pos, expected))
                    command->first = true;
                else if (s_after.ignore(pos, expected))
                {
                    if (!parser_name.parse(pos, command->column, expected))
                        return false;
                }
                command->type = ASTAlterCommand::ADD_COLUMN;
            }
            else if (s_rename_column.ignore(pos, expected))
            {
                if (s_if_exists.ignore(pos, expected))
                    command->if_exists = true;
                if (!parser_name.parse(pos, command->column, expected))
                    return false;
                if (!s_to.ignore(pos, expected))
                    return false;
                if (!parser_name.parse(pos, command->rename_to, expected))