在字段中获取所有元素数的 MySQL 查询?
为此,可以使用 COUNT() 方法。我们首先创建一个表 -
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记录 -
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 语句从表中显示所有记录 -
mysql> select *from DemoTable;
输出
这将生成以下输出 -
+-------------+ | ProductName | +-------------+ | Product-1 | | Product-2 | | Product-3 | | Product-3 | | Product-2 | | Product-4 | | Product-5 | | Product-1 | +-------------+ 8 rows in set (0.00 sec)
以下查询用于获取字段中所有元素的计数 -
mysql> select ProductName,count(ProductName) as TotalCount from DemoTable group by ProductName;
输出
这将生成以下输出 -
+-------------+------------+ | ProductName | TotalCount | +-------------+------------+ | Product-1 | 2 | | Product-2 | 2 | | Product-3 | 2 | | Product-4 | 1 | | Product-5 | 1 | +-------------+------------+ 5 rows in set (0.05 sec)
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