對于數(shù)據(jù)庫來說多多少少要掌握一點,首先基本的SQL語句要了解。下面來總結(jié)一些入門級別的SQL語句。
create相關(guān)
show database; 顯示出現(xiàn)有的數(shù)據(jù)庫
use database_x; 現(xiàn)在要使用數(shù)據(jù)庫database_x
create table coffee (id int(5) not null,coffee_name var25)); 創(chuàng)建一張表,包含id和coffee_name兩個字段
alter table coffee add taste var10); 增加新的一列
into coffee (id,coffee_name,taste,rank) value ("1","BlueMountain",“well”,“5”); 插入數(shù)據(jù)
show columns from coffee; 查看表結(jié)構(gòu)
show create table coffee; 查看表信息,包括建表語句
alter table student rename ss; 改變表名
alter table ss drop mark; 刪除表ss中mark列
select語句
select * from coffee where id="1"; 查詢出id=1的所有信息
select coffee_name from coffee where id="2"; 查詢出id=2的coffee name
select * from club where id between "1" and "3"; 查詢出id=1到3的條目
select * from club where id="1" or id="3"; 查詢出id=1和id=3這兩個條目
select club_name from club where mark>50; 查詢出mark大于50的club
select club_name from club where mark not between 48 and 50; 查詢mark不在48與50之間的club
select * from club where id in("1","3","4"); 查詢id=1,3,4的條目
select * from club where id not in("1","3","4");
select * from club where name like "M%r"; 通配符%表示任意長度的字符(可以是0,漢字為兩個字符)
select * from club where name like "M_r"; _表示單個字符
select * from club where id in("1","3","4") and mark>50; 多重查詢
select * from club order by mark desc; 按照mark降序排列(desc:降序,usc:升序)
數(shù)量查詢相關(guān)
select count(*) from club; 查詢club中有多少條記錄
select count(distinct mark) from club; 不同分?jǐn)?shù)的有多少條記錄
select sum(mark) from club; 積分總和
select avg(mark) from club; 平均積分
select max(mark) from club; 最高積分
select min(mark) from club; 最低積分
update語句
club set mark=mark-8 where id="1"; id=1的俱樂部積分罰8分
語句
from club where id="001"; 刪除id=001的俱樂部信息
以上語句都是SQL語句增刪改查最基本的部分,屬于入門級別,一定要掌握。
[認(rèn)識數(shù)據(jù)庫首先認(rèn)識SQL語句]