What is the difference in syntax between sql and oracle?

The differences between SQL and Oracle syntax are: 1. Different data types; 2. Different functions to obtain the current system time; 3. Different ways of creating users; 4. Different ways of connecting variables and strings ;5. The syntax of the conditional statement "if...else..." is different, etc.

The syntax differences between SQL and Oracle include different data types, different functions to obtain the current system time, no default constraints in Oracle, and the way to connect variables and strings Different, the case statement is different, etc.

The data types are different

SQL server data types: int, smallint, char, varchar, nchar, nvarchar, ntext,datetime,smalldatetime,money,decima,float,bit

Oracle data type: number(p,s),char,varchar2,Date,LOB

Get the current system The functions of time are different

sql server: getdate()

oracle: sysdate

For example: function to set date format

to_char(sysdate,'yyy-mm-dd');

There is no default constraint in oracle

Add default constraint in sql server:

alter table talbe_name add DF_table_name default('男') for sex;

Add default value in oracle:

alter table table_name modify(sex default('男'))；

The methods of connecting variables and strings are different

sql server medium connection: use " " connection, for example:

print 'aaaa'+@name;

oracle medium connection: use "|| "Connection, for example:

dbms_output.put_line('aaa'||name);//name为变量

oracle does not have an identity automatic growth column, but uses a sequence to achieve growth

sql server automatic growth: identity (1,1 can be used directly in the primary key column of the table )Achieve growth

oracle Use the sequence to automatically grow:

create sequence se_id 
start with 1
increment by 1

Use the sequence to realize automatic growth: se_id.nextval

The syntax of the conditional statement if...else... Different

sql server:

  if 条件
            begin
              …………
            end
            else
            begin
              …………
            end

oracle:

  if 条件1 then
               …………;
            elsif 条件2 then
               …………;
            else
              …………;
            end if;

The syntax of case statement is different

sql server In:

select ....case.....（else）....end....语句
            select stuno '学号',case
            when grade>=90 and grade<=100 then &#39;★★★★&#39;
            when grade>=80 and grade<90 then &#39;★★★&#39;
         when grade>=70 and grade<80 then &#39;★★&#39;
         when grade>=60 and grade<70  then &#39;★&#39;
            else &#39;差&#39;
            end as &#39;等级&#39; from score
            go

oracle:

  declare
        nums number:=&nos;--&nos表示提示传入值
            begin
              case nums
                when 100 then
                  dbms_output.put_line('满分也，不错');
                when 90 then
                  dbms_output.put_line('90分页很不错了');
                end case;
            end;

The way to create users is different

sql server

Create login Account: sa-----123456

create Login 登陆名称 with password='登陆密码'

Modify login account:

alter Login 登陆名称 with name='新登录名称' and password='新登录密码'

Disable/enable login account

alter Login 登录名称 disable(禁用)/enable(启用)

Delete login account

drop Login 登录名称

Create user:

create user 用户名 for/from Login 登陆名称

Modify user name

alter user 用户名 with name='新用户名'

Delete user name

drop user 用户名

Authorization limit

grant select/update/delete/insert on 表名 to 用户名

oracle:

Create user syntax

create user 用户名
identified by 密码
default tablespace users
temporary tablespace temp
quota 10M on users

Modify password

alter user 用户名 identified by 新密码

Grant permission

grant create session to 用户名

Delete User

drop user 用户名 cascade;

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