如何计算具有特定值的行（ID），如果MySQL中相同的ID具有其他值，该如何排除呢？

Question

I need to count Companies that have Field_ID "134" but don't have other Field_IDs; in my example Company with ID 2 has only 1 field "134" so I need this to be counted, but company with ID 3 has field "134" but other fields as well, so I want to exclude this one from counting.

Table ID        Company_ID  Field_ID
1               1              130
2               1              131
3               2              134
4               3              134
5               3              137
6               3              140

MySQL Workbench

SELECT count(distinct id) FROM company
where field_id = 1 

I need to count Companies that have Field_ID "134" but don't have other Field_IDs; in my example Company with ID 2 has only 1 field "134" so I need this to be counted, but company with ID 3 has field "134" but other fields as well, so I want to exclude this one from counting.

Expected result should be count of "1"

Table ID        Company_ID  Field_ID
1               1              130
2               1              131
3               2              134
4               3              134
5               3              137
6               3              140

Answer 1

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(Company_ID  INT NOT NULL,Field_ID INT NOT NULL,PRIMARY KEY(company_id,field_id));

INSERT INTO my_table VALUES
(1,130),
(1,131),
(2,134),
(3,134),
(3,137),
(3,140);

SELECT DISTINCT x.* 
           FROM my_table x 
           LEFT 
           JOIN my_table y 
             ON y.company_id = x.company_id 
            AND y.field_id <> x.field_id 
          WHERE x.field_id = 134 
            AND y.company_id IS NULL;
+------------+----------+
| Company_ID | Field_ID |
+------------+----------+
|          2 |      134 |
+------------+----------+

You can also use HAVING MAX(field_id) = 134 AND MIN(field_id) = 134, or variations on that theme

Answer 2

You can group by Company_ID and count the number of Field_ID , then select only the ones that have that count = 1 :

Schema (MySQL v5.7)

CREATE TABLE test (
  `Table ID` INTEGER,
  `Company_ID` INTEGER,
  `Field_ID` INTEGER
);

INSERT INTO test
  (`Table ID`, `Company_ID`, `Field_ID`)
VALUES
  (1, 1, 130),
  (2, 1, 131),
  (3, 2, 134),
  (4, 3, 134),
  (5, 3, 137),
  (6, 3, 140);

---

Query #1

SELECT t.Company_ID
FROM test t
GROUP BY t.Company_ID
HAVING COUNT(t.Field_ID) = 1
AND MAX(t.Field_ID) = 134;

Output

| Company_ID |
| ---------- |
| 2          |

---

View on DB Fiddle