Oracle database knowledge points (IV)

Catalog

One ． Use PL/SQL

Two 、 Cursor management

3、 ... and 、 Subroutines

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One ． Use PL/SQL

Can be used to create stored procedures , trigger , Package , to SQL Add program logic to the execution of the statement .

Support SQL, stay PL/SQL Can be used in ：

Data manipulation command

Transaction control command

slider control

SQL Functions and SQL Operator

Support for object-oriented programming (OOP)

Portability

Better performance ,PL/SQL After compiling and executing

It's divided into three parts ： Declaration part , Executable part and exception handling part

[declare

declarations]

begin

executable statements

[exception

handlers]

end;

Open output

set serverout on;

Two 、 Cursor management

cursor type ： Implicit cursors , Explicit cursors ,REF The cursor

REF Cursors are used to handle dynamic objects that can only be determined at run time SQL Result of query

========== Implicit cursors ==========

stay PL/SQL Use in DML Statement automatically creates an implicit cursor

Implicit cursors automatically declare 、 Open and close , Its name is SQL

Properties of implicit cursors ：

%found                       SQL Statement affects the substance and returns true

%notfound                 SQL The statement returns... After it has no effect on the substance true

%rowcount                SQL The number of lines affected by the statement

%isopen            Whether the cursor is open , Always be false

Example ：

begin

update user_tbl set score=score+5;

if SQL%found then

         dbms_output.put_line(' The data has been changed ： '||SQL%rowcount);

elsif sql%notfound then

         dbms_output.put_line(' No data found ！');

end if;

if SQL%isopen then

         dbms_output.put_line('Open');

else

         dbms_output.put_line('Close');

end if;

end;

========== Explicit cursors ==========

stay PL/SQL The declaration section of defines the query , The query can return multiple rows ：

  declare cursor 、 Open cursor 、  Retrieve data from a cursor 、 Close cursor

Declare that the cursor performs two tasks ：

Name the cursor

Associate a query with a cursor

cursor cursor_name is select statement;

Open cursor ：

  open cursor_name;

Take the data ：   

  fetch cursor_name into record_list;

Close cursor ：      

 close cursor_name;

Explicit cursor properties ：

%found                      Carry out the last one fetch When the statement returns a row successfully, it is true

%notfound                 Carry out the last one fetch Statement fails to return a row true

%rowcount                Returns the number of rows fetched by the cursor so far

%isopen            Whether the cursor is open

Example ：

An explicit cursor with parameters

declare

users user_tbl%rowtype;

cursor boys_cur(sexParam varchar2)

is select * from user_tbl where sex=sexParam;

begin

open boys_cur('&sex');

loop

fetch boys_cur into users;

exit when boys_cur%notfound;

dbms_output.put_line(users.user_name||'  '||users.password);

dbms_output.put_line(boys_cur%rowcount);

end loop;

close boys_cur;

end;

Loop cursor

declare

cursor user_cur is select * from user_tbl;

begin

for username in user_cur loop

         dbms_output.put_line(username.user_name||'  '||username.sex);

end loop;

end;

REF The cursor ：

REF Cursors and cursor variables are used to handle dynamically executed at run time SQL Inquire about

To create a cursor variable ：

a、  Statement REF cursor type

b、 Statement REF Variable of cursor type

Syntax for declaring types

Type ref_cursor_name is ref cursor [return return_type];

Syntax for opening cursor variables

Open cursor_name for select_statement;

Declare strongly typed cursors

declare

type ref_cur is ref cursor return user_tbl%rowtype;

users_cur ref_cur;

Declare weakly typed cursors

declare

type ref_cur is ref cursor;

users_cur ref_cur;

3、 ... and 、 Subroutines

Subroutines are divided into ： Stored procedures and functions , It is named PL/SQL block , Compile and store in the database .

Each part of the subroutine ： Declaration part , The executable part , Exception handling part .

The process ---- Do something

function ---- Perform the operation and return the value

========== stored procedure ==========

The syntax of the creation process ：

create or replace procedure

proce_name (parameter_list)

is|as

local variable declaration

begin

executable statements

exception

exception_handlers

end proce_name;

Three modes of process parameters ：

In---- The value used to receive the call , Default parameter mode

Out---- Used to return a value... To the caller

In out---- Used to receive the value of the calling program , And return the updated value to the caller

The syntax of the execution process ：

Execute proce_name(parameter_list);

or

Declare

Variable var_list;

Begin

Proce_name(var_list);

End;

Grant process execution permission to other users ：

Grant execute on proce_name to scott;

Grant execute on proce_name to public;

Delete stored procedure ：

Drop procedure proce_name;

========== function ==========

The syntax for creating functions ：

Create or replace function

Fun_name (parameter_list)

Return datatype is|as

Local declarations

Begin

Executable statements;

Return result;

Exception

Exce_handlers;

End;

Function can only receive in Parameters , Can't accept out or in out Parameters , Formal parameters cannot be PL/SQL type

The return type of a function must also be a database type

How to access functions ：

a、 Use PL/SQL block

b、 Use SQL sentence

Select fun_name(parameter_list) from dual;