如何对多个查询的结果进行交替排序？

Question

我有一个由三个 select 子句组成的查询，如下所示：

select id, colors from table1
    union all
select id, numbers from table2 
    union all
select id, names from table3

这里还有表格结构：

// table1               // table2              //table3
+----+--------+        +----+---------+        +----+-------+
| id | colors |        | id | numbers |        | id | names |
+----+--------+        +----+---------+        +----+-------+
| 1  | red    |        | 1  | ten     |        | 1  | jack  |
| 2  | green  |        | 2  | two     |        | 2  | peter |
| 3  | blue   |        | 3  | one     |        +----+-------+
| 4  | yellow |        | 4  | three   |
+----+--------+        | 5  | six     |
                       | 6  | five    |
                       +----+---------+

现在我想要这样的结果顺序：

+----+--------+
| id | colors |
+----+--------+
| 1  | red    |
| 2  | ten    |
| 3  | jack   |
| 4  | green  |
| 5  | two    |
| 6  | peter  |
| 7  | blue   |
| 8  | one    |
| 9  | yellow |
| 10 | three  |
| 11 | six    |
| 12 | five   |
+----+--------+

我该如何实施？（需要注意的是，order by 1,2,3对我不起作用）

Answer 1

这就是你如何做到这一点

select @rn:=@rn+1 as id,colors from (
  (select @rn1:= @rn1+1 as rn,colors from table1,(select @rn1:=0)x order by id )
   union all 
  (select @rn2:= @rn2+1 as rn,numbers as colors from table2,(select @rn2:=0.5)x order by id)
   union all 
  (select @rn3:= @rn3+1 as rn,names as colors from table3,(select @rn3:=0.6)x order by id )
)x,(select @rn:=0)y order by rn ;

想法是为每个 table 项分配一个 rn 值，并且需要确保这些值始终按升序排列

因此，如果您运行每个 table 的查询，您将有

mysql> select @rn1:= @rn1+1 as rn,colors from table1,(select @rn1:=0)x order by id;
+------+--------+
| rn   | colors |
+------+--------+
|    1 | red    |
|    2 | green  |
|    3 | blue   |
|    4 | yellow |
+------+--------+
4 rows in set (0.00 sec)

mysql> select @rn2:= @rn2+1 as rn,numbers as colors from table2,(select @rn2:=0.5)x order by id;
+------+--------+
| rn   | colors |
+------+--------+
|  1.5 | ten    |
|  2.5 | two    |
|  3.5 | one    |
|  4.5 | three  |
|  5.5 | six    |
|  6.5 | five   |
+------+--------+
6 rows in set (0.00 sec)

mysql> select @rn3:= @rn3+1 as rn,names as colors from table3,(select @rn3:=0.6)x order by id;
+------+--------+
| rn   | colors |
+------+--------+
|  1.6 | jack   |
|  2.6 | peter  |
+------+--------+
2 rows in set (0.00 sec)

在这里你可以看到 table1 rn 值是 1,2,3,.... table2 值为 1.5,2.5,3.5,.... table3 值为 1.6,2.6,....

所以最后当你用所有 rn 排序结果时它会是

1,1.5,1.6,2,2.5,2.6,....

如何对多个查询的结果进行交替排序？

How to sort the result of multiple queries alternatively?

mysql

sql-order-by

union-all