alter table drop constraint throws an error.

[tvallotton]

Hi, the following test does not pass. I would expect this to work.

use sqlparser::*;

#[test]
fn func() {
    let stmt = "ALTER TABLE table_name DROP CONSTRAINT constr_name;";

    let x = parser::Parser::parse_sql(&dialect::GenericDialect {}, stmt);
    dbg!(x).unwrap();
}

(Also, DropConstraint { name: Ident } should probably also contain fields for cascade/restrict, and possibly if_exists )

[tvallotton]

Note that when constructing the value by hand and transforming it to a string, we get the expected result:

use sqlparser::ast::{AlterTableOperation, Ident, ObjectName, Statement};

#[test]
fn func() {
    let stmt = Statement::AlterTable {
        name: ObjectName(vec![Ident::new("table_name")]),
        operation: AlterTableOperation::DropConstraint {
            name: Ident::new("constraint_name"),
        },
    };
    println!("{}", stmt);
}

ALTER TABLE table_name DROP CONSTRAINT constraint_name

[alamb]

fixed in #396