本文没有对PL/SQL中的东西有什么说明,只是简单的举了几个例子,希望对大家有用!
作者:peace.zhao关于 游标 if,for 的例子
create or replace procedure peace_if
is
cursor var_c is select * from grade;
begin
for temp in var_c loop
if temp.course_name = 'OS' then
dbms_output.put_line('Stu_name = '||temp.stu_name);
elsif temp.course_name = 'DB' then
dbms_output.put_line('DB');
else
dbms_output.put_line('feng la feng la ');
end if;
end loop;
end;
---关于游标 for,case 的例子1
create or replace procedure peace_case1
is
cursor var_c is select * from test_case;
begin
for temp in var_c loop
case temp.vol
when 1 then
dbms_output.put_line('haha1');
when 2 then
dbms_output.put_line('haha2');
when 3 then
dbms_output.put_line('haha3');
when 4 then
dbms_output.put_line('haha4');
else
dbms_output.put_line('qita');
end case ;
end loop;
end;
---关于游标 for,case 的例子2
create or replace procedure peace_case2
is
cursor var_c is select * from test_case;
begin
for temp in var_c loop
case
when temp.vol=1 then
dbms_output.put_line('haha1');
when temp.vol=2 then
dbms_output.put_line('haha2');
when temp.vol=3 then
dbms_output.put_line('haha3');
when temp.vol=4 then
dbms_output.put_line('haha4');
else
dbms_output.put_line('qita');
end case ;
end loop;
end;
---关于for 循环的例子
create or replace procedure peace_for
is
sum1 number :=0;
temp varchar2(500);
begin
for i in 1..9 loop
temp := '';
for j in 1 .. i
loop
sum1 := i * j;
temp := temp||to_char(i) || ' * ' ||to_char(j) ||' = ' ||to_char(sum1) ||' ';
end loop;
dbms_output.put_line(temp );
end loop;
end;
---关于 loop循环的例子
create or replace procedure peace_loop
is
sum1 number := 0;
temp number :=0 ;
begin
loop
exit when temp >= 10 ;
sum1 := sum1+temp;
temp := temp +1;
end loop;
dbms_output.put_line(sum1 );
end;
---关于游标和loop循环的例子
create or replace procedure loop_cur
is
stu_name varchar2(100);
course_name varchar2(100);
cursor var_cur is select * from grade ;
begin
open var_cur;
loop
fetch var_cur into stu_name,course_name;
exit when var_cur%notfound;
dbms_output.put_line(stu_name|| course_name);
end loop;
close var_cur;
end;
---关于异常处理的例子
create or replace procedure peace_exp(in1 in varchar2)
is
c_n varchar2(100);
begin
select course_name into c_n from grade where stu_name = in1;
dbms_output.put_line(c_n);
exception
when no_data_found
then
dbms_output.put_line('try');
when TOO_MANY_ROWS
then
dbms_output.put_line('more');
end;
---关于异常处理的例子2
create or replace procedure peace_insert ( c_n in varchar2)
is
error EXCEPTION;
begin
if c_n = 'OK'
then
insert into course (course_name) values (c_n);
elsif c_n = 'NG' then
insert into course (course_name) values (c_n);
raise error;
else
Dbms_Output.put_line('c_n' || c_n);
end if;
commit;
exception
when error then
rollback;
Dbms_Output.put_line('ERRO');
end;
---关于包的例子 定义包
create or replace package peace_pkg
as
function test1(in1 in varchar2)
return number;
procedure test2 (in2 in varchar2);
end peace_pkg;
---关于包的例子 定义包体
create or replace package body peace_pkg
as
function test1(in1 in varchar2)
return number
as
temp number;
begin
temp := 0;
return temp;
end;
procedure test2 (in2 in varchar2)
is
begin
dbms_output.put_line(in2);
end;
end peace_pkg;

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Common security vulnerabilities in MySQL include SQL injection, weak passwords, improper permission configuration, and unupdated software. 1. SQL injection can be prevented by using preprocessing statements. 2. Weak passwords can be avoided by forcibly using strong password strategies. 3. Improper permission configuration can be resolved through regular review and adjustment of user permissions. 4. Unupdated software can be patched by regularly checking and updating the MySQL version.

Identifying slow queries in MySQL can be achieved by enabling slow query logs and setting thresholds. 1. Enable slow query logs and set thresholds. 2. View and analyze slow query log files, and use tools such as mysqldumpslow or pt-query-digest for in-depth analysis. 3. Optimizing slow queries can be achieved through index optimization, query rewriting and avoiding the use of SELECT*.

To monitor the health and performance of MySQL servers, you should pay attention to system health, performance metrics and query execution. 1) Monitor system health: Use top, htop or SHOWGLOBALSTATUS commands to view CPU, memory, disk I/O and network activities. 2) Track performance indicators: monitor key indicators such as query number per second, average query time and cache hit rate. 3) Ensure query execution optimization: Enable slow query logs, record and optimize queries whose execution time exceeds the set threshold.

The main difference between MySQL and MariaDB is performance, functionality and license: 1. MySQL is developed by Oracle, and MariaDB is its fork. 2. MariaDB may perform better in high load environments. 3.MariaDB provides more storage engines and functions. 4.MySQL adopts a dual license, and MariaDB is completely open source. The existing infrastructure, performance requirements, functional requirements and license costs should be taken into account when choosing.

MySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.

The situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.

In MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.


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