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Oracle數(shù)據(jù)庫開發(fā)必備利器之SQL基礎(chǔ)

難度入門
時長 4小時14分
學習人數(shù)
綜合評分9.67
338人評價 查看評價
9.8 內(nèi)容實用
9.7 簡潔易懂
9.5 邏輯清晰
select * from users;
select * from users where username like 'a%';
select * from users where username like 'a_';
select * from users where username like '_a%';
select * from users where username like '%a%';
select * from users;
select id,username,salary+200 from users;
select * from users;

select username from users where salary>800;

select username from users where salary>800 and salary<>1800.5;
select username form users where salary>800 or salary<>1800.5;
select id as 編號,username as 用戶名,salary 工資 from users;
select distinct username as 用戶名 from users;
select * from users;
col id heading 編號;
col username heading 用戶名;
col salary heading 工資;
select * from users;
select username,salary from users;
col username heading 用戶名;
select * from users;
col username format a10;
select * from users;
col salary format 9999.9;
select * from users;
col salary format 999.9;
select * from users;
col salary format $9999.9;
select * from users;
col username clear;
col salary clear;
select * from users;
alter table userinfo_c3 drop constraint ck_salary_new;
desc salary
select constraint_name,constraint_type,status from user_constraints where table_name='USERINFO_C3';
alter table userinfo_c3 disable constraint ck_salay_new;
select constraint_name,constraint_type,status from user_constraints where table_name='USERINFO_C3';
create table userinfo_c3(id varchar2(10) primary key, username varchar2(20), salary number(5,0));
alter table userinfo_c3 add constraint ck_salary_new check(salary>0);
create table userinfo_c1(id varchar2(10) primary key,username varchar2(20), salary number(5,0),constraint ck_salary chack(salary>0));
create table userinfo_c(id varvhar2(10) primary key, username varchar2(20), salary number(5,0) check(salary>0));
insert into userinfo_c values(1,'aa,-50);
alter table userinfo_u2 drop constraint un_username_new;
select constraint_name,constraint_type,status from user_constraints where table_name='USERINFO_U2';
alter table userinfo_u2 disable constraint un_username_new;
select constraint_name,constraint_type,status from user_constraints where table_name='USERINFO_U2';
create table userinfo_u2(id varchar2(10) primary key,username varchar2(20));
alter table userinfo_u2 add constraint un_username_new unique(username);
create table userinfo_u(id varchar2(10) primary key,username varchar2(20) unique,userpwd varchar2(20));
create table userinfo_u1(id varchar2(10) primary key,username varchar(20),userpwd varchar2(20) ,constrait un_username unique(username));
alter table userinfo_f4 drop constraint fk_typeid_alter;
select constraint_name,constraint_type,status from user_constraints where table_name='USERINFO_F4';
select constraint_name,constraint_type,status from user_constraints where table_name='USERINFO_F4';
alter table userinfo_f4 fisable constraint fk_typeid_alter;
select constraint_name,constraint_type,status from user_constraints where table_name='USERINFO_F4';
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課程須知
只要知道數(shù)據(jù)庫是什么就可以來學習本課程呦！
老師告訴你能學到什么？
掌握Oracle的SQL語句基礎(chǔ)，為后續(xù)的課程學習打好基礎(chǔ)。

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