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法律研究在 MySQL 中計數單獨文字的多個出現？
你可以使用聚合函式 count 和 if() 來實現這個功能。為了理解這個概念，讓我們建立一個表。建立表的查詢如下
mysql> create table CountOccurrencesDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> TechnicalSubject varchar(100) -> ); Query OK, 0 rows affected (0.68 sec)
現在你可以使用 insert 命令在表中插入一些記錄。查詢如下
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 語句顯示錶中的所有記錄。查詢如下
mysql> select *from CountOccurrencesDemo;
輸出如下
+----+------------------+ | 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)
以下是統計 MySQL 中文字多次出現的查詢
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;
輸出如下
+----------------+-----------------+-------------------+ | JavaOccurrence | MySQLOccurrence | MongoDBOccurrence | +----------------+-----------------+-------------------+ | 5 | 3 | 2 | +----------------+-----------------+-------------------+ 1 row in set (0.05 sec)
更新於: 30-Jul-2019
286 次瀏覽
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