นับจำนวนครั้งที่ข้อความต่างๆ ปรากฏใน MySQL

สามารถใช้ฟังก์ชันรวม COUNT ร่วมกับ IF() เพื่อนับจำนวนครั้งที่ข้อความเฉพาะปรากฏได้ เริ่มจากสร้างตารางตัวอย่าง:

mysql> create table CountOccurrencesDemo
    -> (
    -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
    -> TechnicalSubject varchar(100)
    -> );
Query OK, 0 rows affected (0.68 sec)

เพิ่มข้อมูลตัวอย่าง:

mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('Java');
Query OK, 1 row affected (0.14 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('MongoDB');
Query OK, 1 row affected (0.13 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('MySQL');
Query OK, 1 row affected (0.16 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('MySQL');
Query OK, 1 row affected (0.10 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('MySQL');
Query OK, 1 row affected (0.07 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('Java');
Query OK, 1 row affected (0.15 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('Java');
Query OK, 1 row affected (0.10 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('Java');
Query OK, 1 row affected (0.09 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('Java');
Query OK, 1 row affected (0.11 sec)
mysql> insert into CountOccurrencesDemo(TechnicalSubject) values('MongoDB');
Query OK, 1 row affected (0.21 sec)

แสดงข้อมูลทั้งหมด:

mysql> select * from CountOccurrencesDemo;

+----+------------------+
| Id | TechnicalSubject |
+----+------------------+
| 1  | Java             |
| 2  | MongoDB          |
| 3  | MySQL            |
| 4  | MySQL            |
| 5  | MySQL            |
| 6  | Java             |
| 7  | Java             |
| 8  | Java             |
| 9  | Java             |
| 10 | MongoDB          |
+----+------------------+
10 rows in set (0.00 sec)

คำสั่งนับจำนวนครั้งของข้อความหลายค่า:

mysql> select count(if(tbl.TechnicalSubject LIKE '%Java%',1,null)) as JavaOccurrence,
    -> count(if(tbl.TechnicalSubject LIKE '%MySQL%',1,null)) as MySQLOccurrence,
    -> count(if(tbl.TechnicalSubject LIKE '%MongoDB%',1,null)) as MongoDBOccurrence
    -> from CountOccurrencesDemo tbl;

+----------------+-----------------+-------------------+
| JavaOccurrence | MySQLOccurrence | MongoDBOccurrence |
+----------------+-----------------+-------------------+
| 5              | 3               | 2                 |
+----------------+-----------------+-------------------+
1 row in set (0.05 sec)