MySQL UNION - 將兩個單值查詢輸出到不同的列中

Question

我有兩個不同的表，我想從中提取唯一ID的數目。每個單表查詢如下所示

SELECT COUNT(DISTINCT(`uniqueid`)) as `t1ID` FROM `table1` 

和

SELECT COUNT(DISTINCT(`uniqueid`)) as `t2ID` FROM `table2` WHERE `condition`='true' 

我想這兩個查詢合併成一個單一的語句。我知道我可以使用數名從第一查詢作爲列名使用

SELECT COUNT(DISTINCT(`uniqueid`)) as `t1ID` FROM `table1` 
UNION ALL 
SELECT COUNT(DISTINCT(`uniqueid`)) as `t2ID` FROM `table2` WHERE `condition`='true' 

然而，這個輸出是兩個數值分成兩行顯示：

+------+ 
+ t1ID + 
+------+ 
+ 4 + 
+------+ 
+ 5 + 
+------+ 

有沒有辦法讓UNION查詢以相應的計數名稱輸出兩列中的數據？即

+------+------+ 
+ t1ID + t2ID + 
+------+------+ 
+ 4 + 5 + 
+------+------+ 

這樣，這將是一個更容易直接引用的結果，而不是起伏記得在查詢提交的順序。

Answer 1

SELECT (SELECT COUNT(DISTINCT(`uniqueid`)) FROM `table1`) as `t1ID`, 
(SELECT COUNT(DISTINCT(`uniqueid`)) FROM `table2` WHERE `condition`='true') as `t2ID` 

Answer 2

select sub1.t1ID, sub2.t2ID 
from (SELECT uniqueid, COUNT(DISTINCT(`uniqueid`)) as `t1ID` FROM `table1`) sub1 
join (SELECT uniqueid, COUNT(DISTINCT(`uniqueid`)) as `t2ID` FROM `table2` 
     WHERE `condition`='true') sub2 on sub1.uniqueid=sub2.uniqueid 

Answer 3

試試這個

select sum(t1ID) as t1ID 
    , sum(t2ID) as t2ID 
from (
    SELECT COUNT(DISTINCT(`uniqueid`)) as `t1ID`, 0 as `t2ID` FROM `table1` 
    union all 
    SELECT 0 as `t1ID`, COUNT(DISTINCT(`uniqueid`)) as `t2ID` FROM `table2` 
    WHERE `condition`='true' 
) 

Answer 4

select sum(t1ID) as t1ID , sum(t2ID) as t2ID 
(
    SELECT COUNT(DISTINCT(`uniqueid`)) as `t1ID`, 0 as `t2ID` FROM `table1` 
    UNION ALL 
    SELECT 0 as `t1ID` , COUNT(DISTINCT(`uniqueid`)) as `t2ID` FROM `table2` WHERE `condition`='true' 
)t 

確保將派生表的別名，因爲我有t否則你會得到錯誤的

Every derived table must have its own alias 

Answer 5

如果我猜的，你想識別輸出，並知道哪個VA泰倫從哪個表...

一個好的技巧是這個

SELECT COUNT(DISTINCT(`uniqueid`)) as `t1ID`, 't1ID' as 'X' FROM `table1` 
UNION ALL 
SELECT COUNT(DISTINCT(`uniqueid`)) as `t2ID`, 't2ID' as 'X' FROM `table2` WHERE `condition`='true' 

增加，「t1ID」和「T2ID」將出現接近計 值和讀取行時，得到第二值（按名稱X），那麼你可以知道哪個值來自哪個來源。