我需要將來自不同表的幾列合並為一個，以便它們在結果中是獨立的行

Question

資料范例

表格1

Value   component1
1            456

表2

Value   component2 
1            555A

表3

value   component3
 2          356

輸出我得到

Value     component1     component2    component3
1             456             555A
2                                          356

我想要的輸出-單獨的行

Value         component
1               456
1               555A
2               356                   

Answer 1

您可以這樣使用union：

SELECT * FROM TableA
UNION
SELECT * FROM TableB
UNION
SELECT * FROM TableC
UNION
SELECT * FROM TableD

如果需要更多信息，請參考此頁面： use union

Answer 2

您可以使用UNION ALL並使別名與每個表上的參數相同。 請看下面：

SELECT `value`,`component1` as 'component' FROM `table1`
UNION ALL
SELECT `value`,`component2` as 'component' FROM `table2`
UNION ALL
SELECT `value`,`component3` as 'component' FROM `table3`

您需要在要合並的每個表上設置相同的表達式/別名。 如果您想了解更多關於MySQL Union和Union All Operators Primer的信息，請參考此鏈接。

Answer 3

    with cte as 
    (
    Select value from table1
    union 
    Select value from table2
    union 
    Select value from table3
    )
    select cte.value
     , table1.Value as component1
    , table2.Value as component2
    , table3.Value as component3
from cte
left outer join table1 on table1.value = cte.value
left outer join table2 on table2.value = cte.value
left outer join table3 on table3.value = cte.value

Answer 4

關於您到目前為止所說的內容，TO_CHAR可能會有所幫助。

SQL> create table table1 (value number, component1 number);

Table created.

SQL> create table table2 (value number, component2 varchar2(20));

Table created.

SQL> create table table3 (value number, component3 number);

Table created.

SQL> insert all
  2    into table1 values (1, 456)
  3    into table2 values (1, '555A')
  4    into table3 values (2, 356)
  5  select * From dual;

3 rows created.

SQL>
SQL> select t1.value, to_char(t1.component1) component from table1 t1 union
  2  select t2.value, t2.component2                    from table2 t2 union
  3  select t3.value, to_char(t3.component3)           from table3 t3;

     VALUE COMPONENT
---------- ----------------------------------------
         1 456
         1 555A
         2 356

SQL>