Question

出于无法控制的原因，我需要在MYSQL中解析键的所有实例的json列，然后获取最大的实例。假设列名称为json_data，而json看起来像这样：

    {
        list_of_stuff: {
            {
                value_i_want: 1
            },
            {
                value_i_want: 2
            },
            {
                value_i_want: 4
            },
            {
                value_i_want: 3
            }
        }
    }

在哪里我需要获取value_i_want标签的最大值，在这种情况下为4。

现在我有以下代码：

SELECT JSON_EXTRACT(json_data->"$.list_of_stuff", "$**.value_i_want") from table_name;

但是它返回的是JSON数组，当我尝试获取这些数组的最大值时，它只是返回具有最长json数组的行，而不是每个数组的最大值。

感谢您的帮助！

编辑我的MYSQL版本是5.7.25

Answer 1

通过创建临时 json_table 然后找到max（），可以

MYSQL 8.0版。

DB fiddle 创建表Test（id整数，名称json）;

insert into Test(id, name) values(1, '{
  "list_of_stuff": [
    {
      "value_i_want": 1
    },
    {
      "value_i_want": 2
    },
    {
      "value_i_want": 4
    },
    {
      "value_i_want": 3
    }
  ]
}');

SELECT @json_var := cast(JSON_EXTRACT(name->"$.list_of_stuff", "$[*]") as char(200))  from Test;
SELECT max(tt.ac)
     FROM
      JSON_TABLE(
        @json_var,
       "$[*]"
        COLUMNS(
           rowid FOR ORDINALITY,
          ac int PATH "$.value_i_want" 

         )
  ) AS tt;

Answer 2

根据json验证程序，您的json无效，因此我正在考虑以下有效的json：

private void Button2_Click(object sender, EventArgs e)
    {

            cmd.CommandType = CommandType.Text;
            cmd.Connection = conn;

            for (int i = 0; i < dataGridView1.Rows.Count - 1; i++)
            {
                cmd.CommandText = "INSERT INTO tabl(Name_Arabic, CIVILIDD , gender, NATIONALITY, TEL8, TEL7, TEL6, TEL5, TEL4, TEL3, TEL2, TEL1, Work_Adderss, Home_Address, Home_Address2, Name_eng, username, note, Governorate, City, Block, Street, Avenue, House, Floor, flat, address_note, status, confirmation,Irregularities,Irregularities_date)values" +
                "(N'" + dataGridView1.Rows[i].Cells[0].Value + "',N'" + dataGridView1.Rows[i].Cells[1].Value + "',N'" + dataGridView1.Rows[i].Cells[2].Value + "',N'" + dataGridView1.Rows[i].Cells[3].Value + "',N'" + dataGridView1.Rows[i].Cells[4].Value + "',N'" + dataGridView1.Rows[i].Cells[5].Value + "',N'" + dataGridView1.Rows[i].Cells[6].Value + "',N'" + dataGridView1.Rows[i].Cells[7].Value + "',N'" + dataGridView1.Rows[i].Cells[8].Value + "',N'" + dataGridView1.Rows[i].Cells[9].Value + "',N'" + dataGridView1.Rows[i].Cells[10].Value + "',N'" + dataGridView1.Rows[i].Cells[11].Value + "',N'" + dataGridView1.Rows[i].Cells[12].Value + "',N'" + dataGridView1.Rows[i].Cells[13].Value + "',N'" + dataGridView1.Rows[i].Cells[14].Value + "',N'" + dataGridView1.Rows[i].Cells[15].Value + "',N'" + dataGridView1.Rows[i].Cells[16].Value + "',N'" + dataGridView1.Rows[i].Cells[17].Value + "',N'" + dataGridView1.Rows[i].Cells[18].Value + "',N'" + dataGridView1.Rows[i].Cells[19].Value + "',N'" + dataGridView1.Rows[i].Cells[20].Value + "',N'" + dataGridView1.Rows[i].Cells[21].Value + "',N'" + dataGridView1.Rows[i].Cells[22].Value + "',N'" + dataGridView1.Rows[i].Cells[23].Value + "',N'" + dataGridView1.Rows[i].Cells[24].Value + "',N'" + dataGridView1.Rows[i].Cells[25].Value + "',N'" + dataGridView1.Rows[i].Cells[26].Value + "',N'" + dataGridView1.Rows[i].Cells[27].Value + "',N'" + dataGridView1.Rows[i].Cells[28].Value + "',N'" + dataGridView1.Rows[i].Cells[29].Value + "',N'" + dataGridView1.Rows[i].Cells[30].Value + "')";
                conn.Open();
                cmd.ExecuteNonQuery();

                conn.Close();
            }
            MessageBox.Show("saved");

    }

这可以与 mysql 5.7 一起使用：

创建mysql函数以返回最大值，然后可以将此函数与任何选择查询一起使用。 see example

{
  "list_of_stuff": [
    {
      "value_i_want": 1
    },
    {
      "value_i_want": 2
    },
    {
      "value_i_want": 4
    },
    {
      "value_i_want": 3
    }
  ]
}

有没有办法在MYSQL中获得JSON数组的最大值

2 个答案: