**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.
{
                    command->type = ASTAlterCommand::ATTACH_PARTITION;
                }
            }
            else if (s_replace_partition.ignore(pos, expected))
            {
                if (!parser_partition.parse(pos, command->partition, expected))
                    return false;
                if (!s_from.ignore(pos, expected))
                    return false;
                if (!parseDatabaseAndTableName(pos, expected, command->from_database, command->from_table))
                    return false;
                command->replace = true;
                command->type = ASTAlterCommand::REPLACE_PARTITION;
            }
            else if (s_attach_part.ignore(pos, expected))
            {
                if (!parser_string_literal.parse(pos, command->partition, expected))
                    return false;
                command->part = true;
                command->type = ASTAlterCommand::ATTACH_PARTITION;
            }
            else if (s_fetch_partition.ignore(pos, expected))
            {
                if (!parser_partition.parse(pos, command->partition, expected))
                    return false;
                if (!s_from.ignore(pos, expected))
                    return false;
                ASTPtr ast_from;
                if (!parser_string_literal.parse(pos, ast_from, expected))