《MYSQL必知必會》學習筆記(4-8章)
以下為《mysql必然知必會》第4-8章學習筆記,主要涉及查詢的select語句,where語句和like萬用字元。
SELECT語句
1.檢索一列
Select name from products;
2.檢索多列
Select id,name,price fromproducts;
3.檢索所有列
Select * from products;
4.檢索id列(返回唯一值)
Select distinct id from products;
5.檢索name列(返回前5行)
Select name from products limit 5;
6.檢索name列(返回6-10行);
Select name from products limit 5,5;
7.檢索name列,並以name列排序
Select name from products order by name;
8.檢索id ,price,name三列,並以price,name排序,首先按price,再按name。
Select id,price,name from productsorder by price,name;
9.檢索id,price,name三列,並以price降序排列(升序是預設的,ASC)
Select id,price,name fromproducts order by price desc;
10.檢索price列中的最大值
Select price from products order by pricedesc limit 1;
WHERE語句
1. 檢索name,price兩列,只返回price為2.5的行
Select name,price from products where price=2.5;
2.檢索name,price兩列,只返回name為fuse的行
Select name,price from products where name=‘fuse’;
3.檢索name,price兩列,只返回price小於10的行
Select name,price from products where price<10;
4.檢索出不是由id為1003供應商製造的產品
Select id pro_name from products where id<>1003;(或者用!=)
5.檢索價格在5元-10元之間的產品
Select name price from products where pricebetween 5 and 10;
6.檢索價格為空的產品列表
Select name from products where price isnull;
組合WHERE子句
1. 檢索1003供應商製作且價格小於等於10元的所有產品名稱和價格
Select name and price from products whereprice <=10 and id=1003;
2. 檢索1002 或者1003供應商製作的產品名稱和價格
Select name,price from products where id=1002 or id=1003;
Select name,price from products where id in(1002,1003);
3. 檢索除1002,1003供應商之外生產的所有產品名稱和價格;
Select name,price from products where id not in(1002,1003);
LIKE操作符
1.檢索以產品名稱以jet開頭的所有產品的id和name
Select id,name from products where name like‘jet%’;
2.檢索產品名稱以s開頭,e結尾的所有產品
Select name from products where name like‘s%e’;
3.檢索產品名稱第二位到最後一位是ton anvil的產品
Select name from products where name like‘_ton anvil’;
注意%與_的區別:%可以匹配0,1,多個字元,而_僅可以匹配1個字元。