mysql从第2行中选择多行相等

我有两张桌子：

TableA          TableB
ID_A            ID_B
P1              Text
P2
P3
P4

-

-

谢谢尼克，他帮助了我

我得到：

ID_A    P1  P2  P3  P4    ID_B Text
1       7   5   6   6      5    E
1       7   5   6   6      6    F
1       7   5   6   6      6    F
1       7   5   6   6      7    G

我怎么能得到这个

ID_A    P1  P2  P3  P4    ID_B Text
1       7   5   6   6      7    G
1       7   5   6   6      5    E
1       7   5   6   6      6    F
1       7   5   6   6      6    F

1°行P1=ID_B

2°行P2=ID_B

3°行P3=ID_B

4°行P4=ID_B

---

您可以使用

案例

，

当

用于自定义排序顺序。这将在所需的排序中显示结果

 SELECT a.*, b.*
 FROM (SELECT ID_A, P1 AS P FROM TableA
  UNION ALL
  SELECT ID_A, P2 FROM TableA
  UNION ALL
  SELECT ID_A, P3 FROM TableA
  UNION ALL
  SELECT ID_A, P4 FROM TableA) p
 JOIN TableA a ON a.ID_A = p.ID_A
 JOIN TableB b ON b.ID_B = p.P
 ORDER BY CASE b.ID_B
     WHEN 7 THEN 4
     WHEN 5 THEN 3
     ELSE 2
 END DESC

---

发生这种情况是因为

p

值的派生表中没有顺序。为了能够进行排序，我们可以添加另一个表示

P

编号的字段（如

P1

，

P2

等），并按该字段而不是

ID\B

进行排序：

SELECT a.*, b.*
FROM (SELECT 1 AS PNUM, ID_A, P1 AS P FROM TableA
      UNION ALL
      SELECT 2, ID_A, P2 FROM TableA
      UNION ALL
      SELECT 3, ID_A, P3 FROM TableA
      UNION ALL
      SELECT 4, ID_A, P4 FROM TableA) p
JOIN TableA a ON a.ID_A = p.ID_A
JOIN TableB b ON b.ID_B = p.P
ORDER BY a.ID_A, p.PNUM

输出：

ID_A    P1  P2  P3  P4  ID_B    Text
1       7   5   6   6   7       G
1       7   5   6   6   5       E
1       7   5   6   6   6       F
1       7   5   6   6   6       F

---

谢谢你，你是sql语言的天才。我的sql知识是基本的。感谢大家的贡献，但最好的解决办法是尼克。

 SELECT a.*, b.*
 FROM (SELECT ID_A, P1 AS P FROM TableA
  UNION ALL
  SELECT ID_A, P2 FROM TableA
  UNION ALL
  SELECT ID_A, P3 FROM TableA
  UNION ALL
  SELECT ID_A, P4 FROM TableA) p
 JOIN TableA a ON a.ID_A = p.ID_A
 JOIN TableB b ON b.ID_B = p.P
 ORDER BY CASE b.ID_B
     WHEN 7 THEN 4
     WHEN 5 THEN 3
     ELSE 2
 END DESC

SELECT * FROM TableA as a1
left join TableB as b1 on ID_B = p1
union ALL
SELECT * FROM TableA
left join TableB on ID_B = p2
union ALL
SELECT * FROM TableA
left join TableB on ID_B = P3
union ALL
SELECT * FROM TableA
left join TableB on ID_B = p4

SELECT a.*, b.*
FROM (SELECT 1 AS PNUM, ID_A, P1 AS P FROM TableA
      UNION ALL
      SELECT 2, ID_A, P2 FROM TableA
      UNION ALL
      SELECT 3, ID_A, P3 FROM TableA
      UNION ALL
      SELECT 4, ID_A, P4 FROM TableA) p
JOIN TableA a ON a.ID_A = p.ID_A
JOIN TableB b ON b.ID_B = p.P
ORDER BY a.ID_A, p.PNUM

ID_A    P1  P2  P3  P4  ID_B    Text
1       7   5   6   6   7       G
1       7   5   6   6   5       E
1       7   5   6   6   6       F
1       7   5   6   6   6       F