最近開發一個船舶專案，遇到的問題

[問題][6]：一個船舶上物料有很多分類,分類下面還存在分類,分類下面還存在分類，有一些分類下面只存在2級關係分類，有的是3級，有的是4級,如果是最終的類別還要帶具體物料的名字以及基本資訊：

[解決思路][6]：

1.建立表結構

以下為關鍵欄位

2.由於主鍵唯一性,所以parentId放上一類別的主鍵id，依次迴圈放置parentId，然後迴圈查詢出來就行裡,這樣依賴，看似解決了，問題出在查詢這裡，因為存在2級3級4級等不同的依賴關係，查詢要查詢多少次呢？查詢2次不行，4次也不行。

3.然後只能用遞迴查詢來解決問題了，[程式碼如下][6]

4.查詢以json格式傳回前端頁面

{
  "code": "200",
  "message": "OK",
  "data": [
    {
      "displayOrder": 4,
      "status": "NORMAL",
      "createBy
 
": 1,
      "createTime": 1463977621000,
      "updateBy": 0,
      "updateTime": null,
      "version": 0,
      "lastUpdate": 1463977786000,
      "storesId": 10067,
      "storesType": "CATEGORY",
      "code": "WL0002",
      "name": "物料2號",
      "specification": "12×1",
      "description": "沒有描述",
      "unit
 
": "T",
      "parentId": 0,
      "children": [
        {
          "displayOrder": 4,
          "status": "NORMAL",
          "createBy": 1,
          "createTime": 1463987635000,
          "updateBy": 0,
          "updateTime": null,
          "version": 0,
          "lastUpdate": 1463987727000,
          "storesId": 10070,
          "storesType": "CATEGORY",
          "code": "SS0001",
          "name": "物料2號",
          "specification": "12×1",
          "description": "沒有描述",
          "unit": "T",
          "parentId": 10067,
          "children": [
            {
              "displayOrder": 4,
              "status": "NORMAL",
              "createBy": 1,
              "createTime": 1463991922000,
              "updateBy": 0,
              "updateTime": null,
              "version": 0,
              "lastUpdate": 1463991922000,
              "storesId": 10078,
              "storesType": "CATEGORY",
              "code": "SS0011",
              "name": "物料2號",
              "specification": "12×1",
              "description": "沒有描述",
              "unit": "T",
              "parentId": 10070,
              "children": [
                {
                  "displayOrder": 4,
                  "status": "NORMAL",
                  "createBy": 1,
                  "createTime": 1463991946000,
                  "updateBy": 0,
                  "updateTime": null,
                  "version": 0,
                  "lastUpdate": 1463991946000,
                  "storesId": 10079,
                  "storesType": "CATEGORY",
                  "code": "SS0012",
                  "name": "物料2號",
                  "specification": "12×1",
                  "description": "沒有描述",
                  "unit": "T",
                  "parentId": 10078,
                  "children": null
                }
              ]
            }
          ]
        },
        {
          "displayOrder": 4,
          "status": "NORMAL",
          "createBy": 1,
          "createTime": 1463987643000,
          "updateBy": 0,
          "updateTime": null,
          "version": 0,
          "lastUpdate": 1463987732000,
          "storesId": 10071,
          "storesType": "CATEGORY",
          "code": "SS0002",
          "name": "物料2號",
          "specification": "12×1",
          "description": "沒有描述",
          "unit": "T",
          "parentId": 10067,
          "children": null
        }
      ]
    },
    {
      "displayOrder": 4,
      "status": "NORMAL",
      "createBy": 1,
      "createTime": 1463977646000,
      "updateBy": 0,
      "updateTime": null,
      "version": 0,
      "lastUpdate": 1463977787000,
      "storesId": 10068,
      "storesType": "CATEGORY",
      "code": "WL0003",
      "name": "物料2號",
      "specification": "12×1",
      "description": "沒有描述",
      "unit": "T",
      "parentId": 0,
      "children": [
        {
          "displayOrder": 4,
          "status": "NORMAL",
          "createBy": 1,
          "createTime": 1463991817000,
          "updateBy": 0,
          "updateTime": null,
          "version": 0,
          "lastUpdate": 1463991816000,
          "storesId": 10076,
          "storesType": "CATEGORY",
          "code": "SS0009",
          "name": "物料2號",
          "specification": "12×1",
          "description": "沒有描述",
          "unit": "T",
          "parentId": 10068,
          "children": null
        },
        {
          "displayOrder": 4,
          "status": "NORMAL",
          "createBy": 1,
          "createTime": 1463991865000,
          "updateBy": 0,
          "updateTime": null,
          "version": 0,
          "lastUpdate": 1463991864000,
          "storesId": 10077,
          "storesType": "CATEGORY",
          "code": "SS0010",
          "name": "物料2號",
          "specification": "12×1",
          "description": "沒有描述",
          "unit": "T",
          "parentId": 10068,
          "children": null
        }
      ]
    },
    {
      "displayOrder": 4,
      "status": "NORMAL",
      "createBy": 1,
      "createTime": 1463977660000,
      "updateBy": 0,
      "updateTime": null,
      "version": 0,
      "lastUpdate": 1463977790000,
      "storesId": 10069,
      "storesType": "CATEGORY",
      "code": "WL0004",
      "name": "物料2號",
      "specification": "12×1",
      "description": "沒有描述",
      "unit": "T",
      "parentId": 0,
      "children": null
    },
    {
      "displayOrder": 4,
      "status": "NORMAL",
      "createBy": 1,
      "createTime": 1463991048000,
      "updateBy": 0,
      "updateTime": null,
      "version": 0,
      "lastUpdate": 1463991047000,
      "storesId": 10072,
      "storesType": "CATEGORY",
      "code": "SS0003",
      "name": "物料2號",
      "specification": "12×1",
      "description": "沒有描述",
      "unit": "T",
      "parentId": 0,
      "children": null
    },
    {
      "displayOrder": 4,
      "status": "NORMAL",
      "createBy": 1,
      "createTime": 1463991240000,
      "updateBy": 0,
      "updateTime": null,
      "version": 0,
      "lastUpdate": 1463991240000,
      "storesId": 10073,
      "storesType": "CATEGORY",
      "code": "SS0004",
      "name": "物料2號",
      "specification": "12×1",
      "description": "沒有描述",
      "unit": "T",
      "parentId": 0,
      "children": null
    },
    {
      "displayOrder": 4,
      "status": "NORMAL",
      "createBy": 1,
      "createTime": 1463991611000,
      "updateBy": 0,
      "updateTime": null,
      "version": 0,
      "lastUpdate": 1463991611000,
      "storesId": 10074,
      "storesType": "CATEGORY",
      "code": "SS0005",
      "name": "物料2號",
      "specification": "12×1",
      "description": "沒有描述",
      "unit": "T",
      "parentId": 0,
      "children": null
    },
    {
      "displayOrder": 4,
      "status": "NORMAL",
      "createBy": 1,
      "createTime": 1463991811000,
      "updateBy": 0,
      "updateTime": null,
      "version": 0,
      "lastUpdate": 1463991815000,
      "storesId": 10075,
      "storesType": "CATEGORY",
      "code": "SS0008",
      "name": "物料2號",
      "specification": "12×1",
      "description": "沒有描述",
      "unit": "T",
      "parentId": 0,
      "children": null
    }
  ]
}

5.如果有更好的解決思路,可以留言交流。