创建sql查询的方法？答案

【问题标题】：Method to create the sql query?创建sql查询的方法？
【发布时间】：2015-07-03 06:44:13
【问题描述】：

是否可以创建以编程方式创建此 SQL 查询的 java 方法取决于 arrayList 的大小，因为 arrayList 的大小有时是 22？

感谢您的帮助！

private String create_sql_order_query(ArrayList<String> nameNumber) {

String sql_find_order2 = "SELECT s2.stop_id  FROM stops s1"
        + " JOIN stops s2 ON s1.stop_id = s2.stop_id - 1"
        + " WHERE CONCAT(s1.name, s2.name) = CONCAT(?,?)";

String sql_find_order3 = "SELECT s3.stop_id  FROM stops s1"
        + " JOIN stops s2 ON s1.stop_id = s2.stop_id - 1"
        + " JOIN stops s3 ON s2.stop_id = s3.stop_id - 1"
        + " WHERE CONCAT(s1.name, s2.name, s3.name) = CONCAT(?,?,?)";

String sql_find_order4 = "SELECT s4.stop_id  FROM stops s1"
        + " JOIN stops s2 ON s1.stop_id = s2.stop_id - 1"
        + " JOIN stops s3 ON s2.stop_id = s3.stop_id - 1"
        + " JOIN stops s4 ON s3.stop_id = s4.stop_id - 1 "
        + " WHERE CONCAT(s1.name, s2.name, s3.name, s4.name) = CONCAT(?,?,?,?)";

String sql_find_order5 = "SELECT s5.stop_id  FROM stops s1"
        + " JOIN stops s2 ON s1.stop_id = s2.stop_id - 1"
        + " JOIN stops s3 ON s2.stop_id = s3.stop_id - 1"
        + " JOIN stops s4 ON s3.stop_id = s4.stop_id - 1 "
        + " JOIN stops s5 ON s4.stop_id = s5.stop_id - 1"
        + " WHERE CONCAT(s1.name, s2.name, s3.name, s4.name) = CONCAT(?,?,?,?,?)";
  .
  .
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  .
return "";

}

【问题讨论】：

标签： java sql

【解决方案1】：

随意改进，但我想你明白了：

private String createSqlStatement(int size) {
    StringBuilder sb = new StringBuilder();

    sb.append("SELECT s").append(size + 1).append(".stop_id  FROM stops s1 ").append("\n");
    for (int i = 1; i <= size; i++) {
        sb.append("  JOIN stops s").append(i + 1).append(" ON s").append(i).append(".stop_id = s").append(i + 1).append(".stop_id - 1")
                .append("\n");
    }
    sb.append(" WHERE CONCAT(");
    for (int i = 1; i <= size; i++) {
        sb.append("s").append(i).append(".name,");
    }
    sb.deleteCharAt(sb.length() - 1);
    sb.append(") = CONCAT(");
    for (int i = 0; i <= size; i++) {
        sb.append("?,");
    }
    sb.deleteCharAt(sb.length() - 1);
    sb.append(");");

    return sb.toString();

}

【讨论】：

【解决方案2】：

可能不是最有效的方法，但很容易弄清楚......

ArrayList<String> nameNumber = new ArrayList<String>();
        nameNumber.add("foo");
        nameNumber.add("bar");
        nameNumber.add("baz");

        String sql_find_order = "SELECT s" + nameNumber.size() + ".stop_id  FROM stops s1";
        String putInWhere1 = "";
        String putInWhere2 = "";
        for(int i = 0; i < nameNumber.size(); i++) {
            sql_find_order += " JOIN stops s" + (i + 2) + " ON s1.stop_id = s2.stop_id - 1";
            putInWhere1 += ", s" + (i + 1) + ".name";
            putInWhere2 += ", ?";
        }

        sql_find_order += " WHERE CONCAT(" + putInWhere1.substring(2) + ") = CONCAT(" + putInWhere2.substring(2) + ")";
        System.out.println(sql_find_order);

结果

SELECT s3.stop_id  FROM stops s1 JOIN stops s2 ON s1.stop_id = s2.stop_id - 1 JOIN stops s3 ON s1.stop_id = s2.stop_id - 1 JOIN stops s4 ON s1.stop_id = s2.stop_id - 1 WHERE CONCAT(s1.name, s2.name, s3.name) = CONCAT(?, ?, ?)

【讨论】：

我会使用 StringBuilder 而不是字符串连接（请参阅stackoverflow.com/questions/18453458/…）
是的，你是对的。就像我说的那样，这不是最有效的方法，而是一种简单的方法。