1. mysql過濾資料
使用where子句
select prod_name, prod_price from products where prod_price = 2.50;
檢查單個值
select prod_name, prod_price from products where prod_name = 'fuses';
select prod_name, prod_price from products where prod_price < 10;
select prod_name, prod_price from products where prod_price <= 10;
不匹配檢查
select vend_id, prod_name from products where vend_id <> 1003;
select vend_id, prod_name from products where vend_id != 1003;
範圍值檢查
select prod_name, prod_price from products where prod_price between 5 and 10;
空值檢查
select cust_id from customers where cust_email is null;
1. where 執行匹配時預設不區分大小寫
2. is null 判斷空值
2. mysql資料過濾
組合where子句
and操作符
select prod_id, prod_price, prod_name from products where vend_id = 1003 and prod_price <= 10;
or操作符
select prod_name, prod_price, vend_id from products where vend_id = 1002 or vend_id = 1003;
計算次序
select prod_name, prod_price, vend_id from products where vend_id = 1002 or vend_id = 1003 and prod_price >= 10;
in操作符
select prod_name, prod_price, vend_id from products where vend_id in (1002, 1003) order by prod_name;
not操作符
select prod_name, prod_price, vend_id from products where vend_id not in (1002, 1003) order by prod_name;
1. and在計算次序中優先順序高於or
2. in使用的好處
1) 語法清楚更直觀
2) 計算次序更容易管理
3) 比or操作符執行快
4) 可以包含其他select語句，可以更動態地建立where子句
3. not關鍵字
not支援in、between、exists子句取反
3. mysql用萬用字元進行過濾
like操作符
百分號(%)萬用字元
%表示任何字元出現任意次數
select prod_id, prod_name from products where prod_name like '%anvil%';
select prod_id, prod_name from products where prod_name like 's%e';
下劃線(_)萬用字元
_表示任何字元出現一次
select prod_id, prod_name from products where prod_name like '_ ton anvil';
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