Question

使用postgreSQL帮助我按日期选择得分范围内的多个计数

|date|score|
|----|-----|
|12/1|2    |
|12/1|4    |
|12/1|5    |
|12/2|3    |

|date|low0-2|high3-4|perfect|
|----|------|-------|-------|
|12/1|1     |1      |1      |
|12/2|0     |1      |0      |

Answer 1

如果我正确地解释了您的示例，那么第二部分就是您希望从第一部分得到的输出，对吗？

您在这里：

styled.div.attrs(({ x, y, radius }) => ({
  style: {
    transform: `translate(${x - radius}px, ${y - radius}px)`
  }
}))`

生产（用于测试的实际日期）：

import styled from "styled-components";

const Container = styled.div.attrs(({ x, y, radius }) => ({
  style: {
    transform: `translate(${x - radius}px, ${y - radius}px)`
  }
}))`
  cursor: grab;
  position: absolute;
  width: 25px;
  height: 25px;
  background-color: red;
  border-radius: 50%;

  ${({ isDragging }) =>
    isDragging &&
    `
    opacity: 0.8
    cursor: grabbing
  `}
`;

export default Container;

互动示例：https://dbfiddle.uk/?rdbms=postgres_9.6&fiddle=2a7f160954020cdffc799e8a02491dc5

Answer 2

demo:db<>fiddle

您可以使用FILTER子句进行组聚合，这是Postgres的一种特殊方式：

SELECT
    my_date,
    COUNT(score) FILTER (WHERE score BETWEEN 0 AND 2) AS "low0-2",
    COUNT(score) FILTER (WHERE score BETWEEN 3 AND 4) AS "high3-4",
    COUNT(score) FILTER (WHERE score = 5) AS "perfect"
FROM
    scores
GROUP BY my_date
ORDER BY my_date

否则，您可以使用CASE子句采用更多的SQL Standard方法：

SELECT
    my_date,
    SUM(
        CASE 
            WHEN score BETWEEN 0 AND 2 THEN 1
            ELSE 0
        END
    ) AS "low0-2",
    SUM(
        CASE 
            WHEN score BETWEEN 3 AND 4 THEN 1
            ELSE 0
        END
    ) AS "high3-4",
    SUM(
        CASE 
            WHEN score = 5 THEN 1
            ELSE 0
        END
    ) AS "perfect"
FROM
    scores
GROUP BY my_date
ORDER BY my_date

如何编写按日期PostgreSQL选择多重计数组

2 个答案: