[英]SELECT SUM(DISTINCT values) across multiple columns in MYSQL
我有一個包含5列的MySQL表來存儲各種值。 對於表中的每個記錄,5列存儲單個值(大約15個中的一個)。 這是結構的一個例子:
| COL1 | COL2 | COL3 | COL4 | COL5 |
|------|------|------|-------|-------|
| val1 | val3 | val8 | val11 | val14 |
| val2 | val3 | val5 | val9 | val12 |
| val1 | val2 | val6 | val14 | val15 |
| val3 | val5 | val9 | val10 | val12 |
| val2 | val4 | val7 | val11 | val14 |
我想創建一個查詢,對這5列中的每一列的唯一值求和。 結果應顯示5列中存在val1,val2,val3等的總次數。
理想情況下,結果的結構如下:
val | total
_____________________
val1 | 34
val2 | 12
val3 | 23
val4 | 14
val5 | 21
etc | etc
在此先感謝您的幫助,非常感謝。
一種方法: SQL小提琴
SELECT val,
COUNT(*) AS total
FROM (SELECT Col1 AS Val
FROM YourTable
UNION ALL
SELECT Col2 AS Val
FROM YourTable
UNION ALL
SELECT Col3 AS Val
FROM YourTable
UNION ALL
SELECT Col4 AS Val
FROM YourTable
UNION ALL
SELECT Col5 AS Val
FROM YourTable) AS T
GROUP BY val
或者另一個: SQL小提琴
SELECT CASE N
WHEN 1 THEN Col1
WHEN 2 THEN Col2
WHEN 3 THEN Col3
WHEN 4 THEN Col4
WHEN 5 THEN Col5
END AS Val,
COUNT(*) AS total
FROM YourTable
CROSS JOIN (SELECT 1 AS N
UNION ALL
SELECT 2
UNION ALL
SELECT 3
UNION ALL
SELECT 4
UNION ALL
SELECT 5) AS T
GROUP BY Val
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