Question

我在Clojure.java.jdbc

中看到以下示例

(sql/db-do-prepared db "INSERT INTO fruit2 ( name, appearance, cost, grade ) VALUES ( ?, ?, ?, ? )" ["test" "test" 1 1.0])

但是如何将java代码转换为clojure代码。我是clojure的新手，不知道如何传递多个vector

final int numRows = 10000;
    PreparedStatement pstmt = conn
        .prepareStatement("insert into new_order values (?, ?, ?)");
    for (int id = 1; id <= numRows; id++) {
      pstmt.setInt(1, id % 98);
      pstmt.setInt(2, id % 98);
      pstmt.setInt(3, id);
      int count;
      if ((count = pstmt.executeUpdate()) != 1) {
        System.err.println("unexpected update count for a single insert " + count);
        System.exit(2);
      }
      if ((id % 500) == 0) {
        System.out.println("Completed " + id + " inserts ...");
      }
    }

Answer 1

对于多个向量，函数是varargs：

(sql/db-do-prepared db "INSERT INTO fruit2 ( name, appearance, cost, grade ) VALUES ( ?, ?, ?, ? )" ["test" "test" 1 1.0] ["test" "test" 2 3.0])

如果要从列表生成输入，可以使用apply：

(apply sql/db-do-prepared db "INSERT INTO fruit2 ( name, appearance, cost, grade ) VALUES ( ?, ?, ?, ? )" (for [i (range 10)] ["test" "test" i 1.0]))

对于该逻辑的文字复制，您不能使用varargs，因为它不会让您有机会在下一次操作之前检查每个返回值：

(let [num-rows 1000
      success
      (reduce
       (fn [state id]
         (let [values [(mod id 98)
                       (mod id 98)
                       id]
               [result] (sql/do-prepared "insert into test values (?)" values)]
           (if (not= result 1)
             {:ok id}
             (reduced {:error result}))))
       (range 1 (inc num-rows)))]
  (if-let [id (:ok success)]
    (println "Completed" id "inserts")
    (do (println "unexpected update count for a single insert" (:error success))
        (System/exit 2))))

Answer 2

就我而言，我认为@noisesmith是正确的，除了我认为sql-params应该在集合（向量）中。

（SQL / DB-DO-制备 D b [“INSERT INTO fruit2（名称，外观，成本，等级）VALUES（？，？，？，？）” “测试”“测试”1 1.0]）

我认为这对我有用（我错过了什么请告诉我）

或者自2013年以来API可能已更改

Clojure db-do-prepared with multiple parameters

2 个答案: