如何找出表的每一列的唯一值计数

Question

我想计算下表中每一列的唯一值。对于每个唯一值，输出应该有 1 行，列数与起始表相同，每个列都有该唯一值的计数：

表名:- mytable

+---------+---------+---------+---------+---------+
| column1 | column2 | column3 | column4 | column5 |
+---------+---------+---------+---------+---------+
| car     | train   | plane   | tempo   | laptop  |
| bike    | pen     | car     | Null    | pencil  |
| tempo   | book    | car     | laptop  | book    |
| Null    | bike    | tempo   | book    | pen     |
+---------+---------+---------+---------+---------+

预期输出：

+---------+---------+---------+---------+---------+---------+
|         | column1 | column2 | column3 | column4 | column5 |
+---------+---------+---------+---------+---------+---------+
| car     |    1    |    0    |    2    |    0    |    0    |
| bike    |    1    |    1    |    0    |    0    |    0    |
| tempo   |    1    |    0    |    1    |    1    |    0    |
| train   |    0    |    1    |    0    |    0    |    0    |
| pen     |    0    |    1    |    0    |    0    |    1    |
| book    |    0    |    1    |    0    |    1    |    1    |
| plane   |    0    |    0    |    1    |    0    |    0    |
| laptop  |    0    |    0    |    0    |    1    |    1    |
| pencil  |    0    |    0    |    0    |    0    |    1    |
| (null)  |    1    |    0    |    0    |    1    |    0    |
+---------+---------+---------+---------+---------+---------+

Answer 1

我希望，这就是你最终要寻找的东西。 一切顺利:)

SQL Fiddle

MySQL 5.5 架构设置：

CREATE TABLE table_name
(
  column_1 VARCHAR (20),
  column_2 VARCHAR (20),
  column_3 VARCHAR (20),
  column_4 VARCHAR (20),
  column_5 VARCHAR (20));

 insert into table_name values
('car','train','plane','tempo','laptop'); 
 insert into table_name values
('bike','pen','car',Null,'pencil'); 
 insert into table_name values
('tempo','book','car','laptop','book'); 
 insert into table_name values
(Null,'bike','tempo','book','pen'); 

查询 1：

SELECT
     valuex,
     SUM(IFNULL(ELT(FIELD(Columnx, 'Column_1'), 1), 0)) as Column_1,
     SUM(IFNULL(ELT(FIELD(Columnx, 'Column_2'), 1), 0)) as Column_2,
     SUM(IFNULL(ELT(FIELD(Columnx, 'Column_3'), 1), 0)) as Column_3,
     SUM(IFNULL(ELT(FIELD(Columnx, 'Column_4'), 1), 0)) as Column_4,
     SUM(IFNULL(ELT(FIELD(Columnx, 'Column_5'), 1), 0)) as Column_5
FROM (
  SELECT column_1 AS valuex, "Column_1" AS Columnx
  FROM table_name
  UNION ALL
  SELECT column_2 AS valuex, "Column_2" AS Columnx
  FROM table_name
  UNION ALL
  SELECT column_3 AS valuex, "Column_3" AS Columnx
  FROM table_name
  UNION ALL
  SELECT column_4 AS valuex, "Column_4" AS Columnx
  FROM table_name
  UNION ALL
  SELECT column_5 AS valuex, "Column_5" AS Columnx
  FROM table_name
) s
group by valuex

Results：

|--------|----------|----------|----------|----------|----------|
| valuex | Column_1 | Column_2 | Column_3 | Column_4 | Column_5 |
|--------|----------|----------|----------|----------|----------|
| (null) |        1 |        0 |        0 |        1 |        0 |
|   bike |        1 |        1 |        0 |        0 |        0 |
|   book |        0 |        1 |        0 |        1 |        1 |
|    car |        1 |        0 |        2 |        0 |        0 |
| laptop |        0 |        0 |        0 |        1 |        1 |
|    pen |        0 |        1 |        0 |        0 |        1 |
| pencil |        0 |        0 |        0 |        0 |        1 |
|  plane |        0 |        0 |        1 |        0 |        0 |
|  tempo |        1 |        0 |        1 |        1 |        0 |
|  train |        0 |        1 |        0 |        0 |        0 |

Answer 2

这是你要找的吗？

SQL Fiddle

MySQL 5.5 架构设置：

CREATE TABLE table_name
(
  column_1 VARCHAR (20),
  column_2 VARCHAR (20),
  column_3 VARCHAR (20),
  column_4 VARCHAR (20),
  column_5 VARCHAR (20));

 insert into table_name values
('car','train','plane','tempo','laptop'); 
 insert into table_name values
('bike','pen','car',Null,'pencil'); 
 insert into table_name values
('tempo','book','car','laptop','book'); 
 insert into table_name values
(Null,'bike','tempo','book','pen'); 

查询 1：

select col, Count(*) from ( 
select distinct column_1 as col from table_name
union all
select distinct column_2 as col from table_name
union all
select distinct column_3 as col from table_name
union all
select distinct column_4 as col from table_name
union all
select distinct column_5 as col from table_name) as newTable
group by col

Results：

|    col | Count(*) |
|--------|----------|
| (null) |        2 |
|   bike |        2 |
|   book |        3 |
|    car |        2 |
| laptop |        2 |
|    pen |        2 |
| pencil |        1 |
|  plane |        1 |
|  tempo |        3 |
|  train |        1 |

Answer 3

按照@fthiella 的逻辑，这里就是答案，我相信这就是你真正想要的 :)

SQL Fiddle

MySQL 5.5 架构设置：

CREATE TABLE table_name
(
  column_1 VARCHAR (20),
  column_2 VARCHAR (20),
  column_3 VARCHAR (20),
  column_4 VARCHAR (20),
  column_5 VARCHAR (20));

 insert into table_name values
('car','train','plane','tempo','laptop'); 
 insert into table_name values
('bike','pen','car',Null,'pencil'); 
 insert into table_name values
('tempo','book','car','laptop','book'); 
 insert into table_name values
(Null,'bike','tempo','book','pen'); 

查询 1：

SELECT valueX, columnX, COUNT(*)
FROM (
  SELECT column_1 AS valuex, "Column_1" AS Columnx
  FROM table_name
  UNION ALL
  SELECT column_2 AS valuex, "Column_2" AS Columnx
  FROM table_name
  UNION ALL
  SELECT column_3 AS valuex, "Column_3" AS Columnx
  FROM table_name
  UNION ALL
  SELECT column_4 AS valuex, "Column_4" AS Columnx
  FROM table_name
) s
GROUP BY valuex, columnX
ORDER BY valuex, columnX

Results：

| valuex |  Columnx | COUNT(*) |
|--------|----------|----------|
| (null) | Column_1 |        1 |
| (null) | Column_4 |        1 |
|   bike | Column_1 |        1 |
|   bike | Column_2 |        1 |
|   book | Column_2 |        1 |
|   book | Column_4 |        1 |
|    car | Column_1 |        1 |
|    car | Column_3 |        2 |
| laptop | Column_4 |        1 |
|    pen | Column_2 |        1 |
|  plane | Column_3 |        1 |
|  tempo | Column_1 |        1 |
|  tempo | Column_3 |        1 |
|  tempo | Column_4 |        1 |
|  train | Column_2 |        1 |

Answer 4

鉴于上表并假设，您想找到 column1 的不同值，这是一个起点：

SELECT column1, count(column1) FROM myTable GROUP BY column1

sqlfiddle here

所有列和一个联合：

SELECT col, count(col) FROM (
  SELECT column1 as col FROM myTable  UNION ALL
  SELECT column2 as col FROM myTable  UNION ALL
  SELECT column3 as col FROM myTable  UNION ALL
  SELECT column4 as col FROM myTable  UNION ALL
  SELECT column5 as col FROM myTable  
) as x GROUP BY x.col

新sqlfiddle

Answer 5

您的表格看起来没有标准化，所以我认为您应该使用更好的结构，但没有任何上下文我不能建议您如何改进它。要解决您的问题，您可以使用一些 UNION ALL 查询，然后使用 GROUP BY

SELECT value, column, COUNT(*)
FROM (
  SELECT column1 AS value, "Column1" AS Column
  FROM mytable
  UNION ALL
  SELECT column2 AS value, "Column2" AS Column
  FROM mytable
  UNION ALL
  SELECT column3 AS value, "Column3" AS Column
  FROM mytable
  UNION ALL
  SELECT column4 AS value, "Column4" AS Column
  FROM mytable
) s
GROUP BY value, column
ORDER BY value, column

如果你想在列中包含所有值，那么你可以使用这个：

SELECT
  value,
  MAX(CASE WHEN column='Column1' THEN cnt END AS cnt_1,
  MAX(CASE WHEN column='Column2' THEN cnt END AS cnt_2,
  MAX(CASE WHEN column='Column3' THEN cnt END AS cnt_3,
  MAX(CASE WHEN column='Column4' THEN cnt END AS cnt_4
FROM (
  SELECT value, column, COUNT(*) AS cnt
  FROM (
    SELECT column1 AS value, "Column1" AS Column
    FROM mytable
    UNION ALL
    SELECT column2 AS value, "Column2" AS Column
    FROM mytable
    UNION ALL
    SELECT column3 AS value, "Column3" AS Column
    FROM mytable
    UNION ALL
    SELECT column4 AS value, "Column4" AS Column
    FROM mytable
  ) AS s
  GROUP BY value, column
  ORDER BY value, column
) AS s
GROUP BY value