資料結構
網路
RDBMS
作業系統
Java
MS Excel
iOS
HTML
CSS
安卓
Python
C 程式設計
C++
C#
MongoDB
MySQL
Javascript
PHP
物理學
化學
生物學
數學
英語
經濟學
心理學
社會科學
時尚研究
法律研究從具有重複值的資料表中選擇 MySQL 中出現次數最多的條目？
讓我們首先建立一個表 −
mysql> create table DemoTable610 (SubjectName varchar(100)); Query OK, 0 rows affected (0.63 sec)
使用插入命令在表中插入一些記錄 −
mysql> insert into DemoTable610 values('MySQL');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable610 values('Java');
Query OK, 1 row affected (0.23 sec)
mysql> insert into DemoTable610 values('MySQL');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable610 values('MongoDB');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable610 values('MySQL');
Query OK, 1 row affected (0.23 sec)
mysql> insert into DemoTable610 values('MySQL');
Query OK, 1 row affected (0.08 sec)
mysql> insert into DemoTable610 values('Java');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable610 values('MongoDB');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable610 values('C');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable610 values('C++');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable610 values('MongoDB');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable610 values('MySQL');
Query OK, 1 row affected (0.21 sec)
mysql> insert into DemoTable610 values('Java');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable610 values('Python');
Query OK, 1 row affected (0.08 sec)
mysql> insert into DemoTable610 values('MySQL');
Query OK, 1 row affected (0.15 sec)使用 select 語句從表中顯示所有記錄 −
mysql> select *from DemoTable610;
這將產生以下輸出 −
+-------------+ | SubjectName | +-------------+ | MySQL | | Java | | MySQL | | MongoDB | | MySQL | | MySQL | | Java | | MongoDB | | C | | C++ | | MongoDB | | MySQL | | Java | | Python | | MySQL | +-------------+ 15 rows in set (0.00 sec)
以下是僅選擇 Top 個顯示次數最多的條目的查詢 −
mysql> select SubjectName from ( select SubjectName from DemoTable610 group by SubjectName order by count(SubjectName) DESC LIMIT 2 ) AS tbl order by SubjectName;
這將產生以下輸出 −
+-------------+ | SubjectName | +-------------+ | Java | | MySQL | +-------------+ 2 rows in set (0.04 sec)
更新於： 22-Aug-2019
82 瀏覽次數
廣告