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法律研究僅顯示出現在 MySQL 中至少三次以上的重複列名稱
為此請使用 HAVING COUNT()。我們先建立一個表 -
mysql> create table DemoTable1351 -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(40) -> ); Query OK, 0 rows affected (1.08 sec)
使用插入命令向表中插入一些記錄 -
mysql> insert into DemoTable1351(StudentName) values('Chris');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable1351(StudentName) values('Mike');
Query OK, 1 row affected (0.68 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.12 sec)使用 select 語句從表中顯示所有記錄 -
mysql> select * from DemoTable1351;
這會生成以下輸出 -
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 1 | Chris | | 2 | Bob | | 3 | Bob | | 4 | David | | 5 | Bob | | 6 | David | | 7 | Bob | | 8 | Mike | | 9 | David | +-----------+-------------+ 9 rows in set (0.00 sec)
以下是對出現在至少三次的重複列名稱的顯示查詢 -
mysql> select * from DemoTable1351 -> group by StudentName -> having count(StudentName) >=3;
這會生成以下輸出 -
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 2 | Bob | | 4 | David | +-----------+-------------+ 2 rows in set (0.00 sec)
更新於： 2019-11-05
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