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Legal Studies在欄位中獲取所有元素數的 MySQL 查詢？
為此，可以使用 COUNT() 方法。我們首先建立一個表 -
mysql> create table DemoTable -> ( -> ProductName varchar(100) -> ); Query OK, 0 rows affected (0.59 sec)
使用 insert 命令在表中插入一些記錄 -
mysql> insert into DemoTable values('Product-1');
Query OK, 1 row affected (0.26 sec)
mysql> insert into DemoTable values('Product-2');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values('Product-3');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values('Product-3');
Query OK, 1 row affected (0.29 sec)
mysql> insert into DemoTable values('Product-2');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values('Product-4');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values('Product-5');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values('Product-1');
Query OK, 1 row affected (0.11 sec)使用 select 語句從表中顯示所有記錄 -
mysql> select *from DemoTable;
輸出
這將生成以下輸出 -
+-------------+ | ProductName | +-------------+ | Product-1 | | Product-2 | | Product-3 | | Product-3 | | Product-2 | | Product-4 | | Product-5 | | Product-1 | +-------------+ 8 rows in set (0.00 sec)
以下查詢用於獲取欄位中所有元素的計數 -
mysql> select ProductName,count(ProductName) as TotalCount from DemoTable group by ProductName;
輸出
這將生成以下輸出 -
+-------------+------------+ | ProductName | TotalCount | +-------------+------------+ | Product-1 | 2 | | Product-2 | 2 | | Product-3 | 2 | | Product-4 | 1 | | Product-5 | 1 | +-------------+------------+ 5 rows in set (0.05 sec)
更新於:30-06-2020
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