使用sql查询在datatable中插入数据

我的查询如下：select id、reffid、myTable中的someData：

id reffid someData 8 10 text1 9 10 text2 10 11 text3 11 11 text4 12 11 text5 13 11 text6 14 12 text7 15 12 text8 16 12 text9 17 13 text10 18 14 text11 我需要执行以下操作的查询：如果具有相同值的reffid少于4个，则添加具有相同reffid的行，并在someData中添加-。结果查询应如下所示：

id reffid someData 8 10 text1 9 10 text2 ??? 10 - ??? 10 - 10 11 text3 11 11 text4 12 11 text5 13 11 text6 14 12 text7 15 12 text8 16 12 text9 ??? 12 - 17 13 text10 ??? 13 - ??? 13 - ??? 13 - 18 14 text11 ??? 14 - ??? 14 - ??? 14 - 如何做到这一点？

试试看

SELECT t.id, l.reffid, COALESCE(t.somedata, '-') someData
  FROM
(
  SELECT reffid, rnum
    FROM
  (
    SELECT DISTINCT reffid
      FROM table1
  ) q CROsS JOIN 
  (
    SELECT 1 rnum UNION ALL
    SELECT 2 UNION ALL
    SELECT 3 UNION ALL
    SELECT 4
  ) n
) l LEFT JOIN 
(
  SELECT id, reffid, somedata, 
         ROW_NUMBER() OVER (PARTITION BY reffid ORDER BY id) rnum
    FROM table1
) t
   ON l.reffid = t.reffid
  AND l.rnum   = t.rnum

输出：

| ID | REFFID | SOMEDATA | |--------|--------|----------| | 8 | 10 | text1 | | 9 | 10 | text2 | | (null) | 10 | - | | (null) | 10 | - | | 10 | 11 | text3 | | 11 | 11 | text4 | | 12 | 11 | text5 | | 13 | 11 | text6 | | 14 | 12 | text7 | | 15 | 12 | text8 | | 16 | 12 | text9 | | (null) | 12 | - | | 17 | 13 | text10 | | (null) | 13 | - | | (null) | 13 | - | | (null) | 13 | - | | 18 | 14 | text11 | | (null) | 14 | - | | (null) | 14 | - | | (null) | 14 | - | 这里是演示

试试看

SELECT t.id, l.reffid, COALESCE(t.somedata, '-') someData
  FROM
(
  SELECT reffid, rnum
    FROM
  (
    SELECT DISTINCT reffid
      FROM table1
  ) q CROsS JOIN 
  (
    SELECT 1 rnum UNION ALL
    SELECT 2 UNION ALL
    SELECT 3 UNION ALL
    SELECT 4
  ) n
) l LEFT JOIN 
(
  SELECT id, reffid, somedata, 
         ROW_NUMBER() OVER (PARTITION BY reffid ORDER BY id) rnum
    FROM table1
) t
   ON l.reffid = t.reffid
  AND l.rnum   = t.rnum

输出：

| ID | REFFID | SOMEDATA | |--------|--------|----------| | 8 | 10 | text1 | | 9 | 10 | text2 | | (null) | 10 | - | | (null) | 10 | - | | 10 | 11 | text3 | | 11 | 11 | text4 | | 12 | 11 | text5 | | 13 | 11 | text6 | | 14 | 12 | text7 | | 15 | 12 | text8 | | 16 | 12 | text9 | | (null) | 12 | - | | 17 | 13 | text10 | | (null) | 13 | - | | (null) | 13 | - | | (null) | 13 | - | | 18 | 14 | text11 | | (null) | 14 | - | | (null) | 14 | - | | (null) | 14 | - |

---

下面是演示

您使用的是哪种DBMS？博士后？Oracle？您使用的是哪种数据库管理系统？博士后？神谕