在 MySQL 中计算单独文本的多次出现次数?
mysqlmysqli database
您可以使用聚合函数 count 和 if() 来实现此目的。为了理解这个概念，让我们创建一个表。创建表的查询如下
mysql> create table CountOccurrencesDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> TechnicalSubject varchar(100) -> ); Query OK, 0 rows affected (0.68 sec)
现在您可以使用insert命令在表中插入一些记录。查询如下
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)
使用 select 语句显示表中的所有记录。查询如下
mysql> select *from CountOccurrencesDemo;
以下是输出 −
+----+------------------+ | 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)
以下是在 MySQL 中计算文本多次出现的查询
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;
以下是输出 −
+----------------+-----------------+-------------------+ | JavaOccurrence | MySQLOccurrence | MongoDBOccurrence | +----------------+-----------------+-------------------+ | 5 | 3 | 2 | +----------------+-----------------+-------------------+ 1 row in set (0.05 sec)
