Suggestions on Database Field Length for Migration

Motivation

The current definition of the length and name of the database field is not in one position, and when the name and length are modified, it is very inconvenient to modify the name and length.

Proposed Solutions

Suggestions be changed to the following

#[async_trait::async_trait]
impl MigrationTrait for Migration {
    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
        manager
            .create_table(
                Table::create()
                    .table(SysApp::Table)
                    .if_not_exists()
                    .col(string(SysApp::AppId).primary_key())
                    .col(string_uniq(SysApp::AppCode, 255))
                    .col(string_uniq(SysApp::AppName, 255))
                    .col(string_null(SysApp::AppDesc, 255))
                    .col(string_null(SysApp::AppUrl))
                    .index(
                        Index::create().unique()
                            .name("UK_SYS_APP_CODE")
                            .col(SysApp::AppCode)
                    )
                    .to_owned(),
            )
            .await?;
    }
}

#[derive(DeriveIden)]
pub enum SysApp {
    #[sea_orm(iden = "SYS_APP")]
    Table,
    #[sea_orm(iden = "APP_ID", len=36)]
    AppId,
    #[sea_orm(iden = "APP_CODE", len=255)]
    AppCode,
    #[sea_orm(iden = "APP_NAME", len=255)]
    AppName,
    #[sea_orm(iden = "APP_DESC", len=255)]
    AppDesc,
    #[sea_orm(iden = "APP_URL")]
    AppUrl,
}

Additional Information

The current definition is as follows:

#[async_trait::async_trait]
impl MigrationTrait for Migration {
    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
        manager
            .create_table(
                Table::create()
                    .table(SysApp::Table)
                    .if_not_exists()
                    .col(string_len(SysApp::AppId, 36).primary_key())
                    .col(string_len_uniq(SysApp::AppCode, 255))
                    .col(string_len_uniq(SysApp::AppName, 255))
                    .col(string_len_null(SysApp::AppDesc, 255))
                    .col(string_null(SysApp::AppUrl))
                    .index(
                        Index::create().unique()
                            .name("UK_SYS_APP_CODE")
                            .col(SysApp::AppCode)
                    )
                    .to_owned(),
            )
            .await?;
}

#[derive(DeriveIden)]
pub enum SysApp {
    #[sea_orm(iden = "SYS_APP")]
    Table,
    #[sea_orm(iden = "APP_ID")]
    AppId,
    #[sea_orm(iden = "APP_CODE")]
    AppCode,
    #[sea_orm(iden = "APP_NAME")]
    AppName,
    #[sea_orm(iden = "APP_DESC")]
    AppDesc,
    #[sea_orm(iden = "APP_URL")]
    AppUrl,
}

Review the migration API around MigrationTrait, SchemaManager, Table::create, the string_len helpers, and DeriveIden attributes. Compare the proposed centralized length declarations with the current migration example, then determine the required API and derive-macro changes. Done means field names and lengths can be maintained in one place while preserving the shown table and index behavior.