SELECT 中的 MySQL 条件 SELECT

Question

Table:

id    price    is_active
========================
1     20.99    0
2     10.99    1
3     30.99    0
4     15.99    1
5     35.99    1

I am trying to select COUNT of all rows that has is_active equals to 1, so I've used this simple query:

SELECT COUNT(*) FROM table WHERE is_active=1

But what if I want to also know how many rows have price:

• less than 15
• between 15 and 30
• more than 30

I can write this:

SELECT COUNT(*) FROM table WHERE is_active=1 AND price < 15
SELECT COUNT(*) FROM table WHERE is_active=1 AND price > 15 AND price < 30
SELECT COUNT(*) FROM table WHERE is_active=1 AND price > 30

But can I do it in one simple query that returns something like this?

"Less than 15" | "Between 15 and 30" | "More than 30"
1              | 2                   | 2

Answer 1

With conditional aggregation:

SELECT 
  SUM(price < 15) `Less than 15`,
  SUM(price >= 15 AND price <= 30) `Between 15 and 30`,
  SUM(price > 30) `More than 30`
FROM `table` 
WHERE is_active=1

In MySql a boolean expression like price < 15 is evaluated as 0 for false or 1 for true .
See the demo .
Results:

| Less than 15 | Between 15 and 30 | More than 30 |
| ------------ | ----------------- | ------------ |
| 1            | 1                 | 1            |

Answer 2

Because they are even intervals you could

SELECT
   IF(price > 30, 30, price) div 15 as g,
   count(*) as c
FROM `table`
WHERE is_active=1
GROUP BY g

Note this leaves 30 in the 'more than 30' category