创建表

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要在数据库中创建表，你可以使用 Schema::create_table_from_entity 从 Entity 派生，而不是手动编写 TableCreateStatement。此方法将帮助你创建包括 Entity 中定义的所有列和外键约束的数据库表。

下面我们使用 CakeFillingPrice entity 演示其生成的 SQL 语句。你可以使用 TableCreateStatement 构建相同的语句。

注意，自 0.7.0 版本起，Schema::create_table_from_entity 不再创建 index。如果需要在数据库中创建 index，请查看此处了解详情。

use sea_orm::{sea_query::*, tests_cfg::*, EntityName, Schema};

let builder = db.get_database_backend();
let schema = Schema::new(builder);

assert_eq!(
    builder.build(&schema.create_table_from_entity(CakeFillingPrice)),
    builder.build(
        &Table::create()
            .table(CakeFillingPrice.table_ref())
            .col(integer(cake_filling_price::Column::CakeId))
            .col(integer(cake_filling_price::Column::FillingId))
            .col(decimal(cake_filling_price::Column::Price))
            .primary_key(
                Index::create()
                    .name("pk-cake_filling_price")
                    .col(cake_filling_price::Column::CakeId)
                    .col(cake_filling_price::Column::FillingId)
                    .primary(),
            )
            .foreign_key(
                ForeignKeyCreateStatement::new()
                    .name("fk-cake_filling_price-cake_id-filling_id")
                    .from_tbl(CakeFillingPrice)
                    .from_col(cake_filling_price::Column::CakeId)
                    .from_col(cake_filling_price::Column::FillingId)
                    .to_tbl(CakeFilling)
                    .to_col(cake_filling::Column::CakeId)
                    .to_col(cake_filling::Column::FillingId),
            )
            .to_owned()
    )
);

为了进一步说明，我们将在下面以字符串形式展示 SQL 语句。

• PostgreSQL

  use sea_orm::{tests_cfg::*, DbBackend, Schema, Statement};
  
  let db_postgres = DbBackend::Postgres;
  let schema = Schema::new(db_postgres);
  
  assert_eq!(
      db_postgres.build(&schema.create_table_from_entity(CakeFillingPrice)),
      Statement::from_string(
          db_postgres,
          [
              r#"CREATE TABLE "public"."cake_filling_price" ("#,
              r#""cake_id" integer NOT NULL,"#,
              r#""filling_id" integer NOT NULL,"#,
              r#""price" decimal NOT NULL,"#,
              r#"CONSTRAINT "pk-cake_filling_price" PRIMARY KEY ("cake_id", "filling_id"),"#,
              r#"CONSTRAINT "fk-cake_filling_price-cake_id-filling_id" FOREIGN KEY ("cake_id", "filling_id") REFERENCES "cake_filling" ("cake_id", "filling_id")"#,
              r#")"#,
          ]
          .join(" ")
      )
  );

• MySQL

  use sea_orm::{tests_cfg::*, DbBackend, Schema, Statement};
  
  let db_mysql = DbBackend::MySql;
  let schema = Schema::new(db_mysql);
  
  assert_eq!(
      db_mysql.build(&schema.create_table_from_entity(CakeFillingPrice)),
      Statement::from_string(
          db_mysql,
          [
              "CREATE TABLE `cake_filling_price` (",
              "`cake_id` int NOT NULL,",
              "`filling_id` int NOT NULL,",
              "`price` decimal NOT NULL,",
              "PRIMARY KEY `pk-cake_filling_price` (`cake_id`, `filling_id`),",
              "CONSTRAINT `fk-cake_filling_price-cake_id-filling_id` FOREIGN KEY (`cake_id`, `filling_id`) REFERENCES `cake_filling` (`cake_id`, `filling_id`)",
              ")",
          ]
          .join(" ")
      )
  );

• SQLite

  use sea_orm::{tests_cfg::*, DbBackend, Schema, Statement};
  
  let db_sqlite = DbBackend::Sqlite;
  let schema = Schema::new(db_sqlite);
  
  assert_eq!(
      db_sqlite.build(&schema.create_table_from_entity(CakeFillingPrice)),
      Statement::from_string(
          db_sqlite,
          [
              "CREATE TABLE `cake_filling_price` (",
              "`cake_id` integer NOT NULL,",
              "`filling_id` integer NOT NULL,",
              "`price` real NOT NULL,",
              "CONSTRAINT `pk-cake_filling_price`PRIMARY KEY (`cake_id`, `filling_id`),",
              "FOREIGN KEY (`cake_id`, `filling_id`) REFERENCES `cake_filling` (`cake_id`, `filling_id`)",
              ")",
          ]
          .join(" ")
      )
  );