Oracle Learning (eight) Pl/sql Introduction, BASIC program structure and statements

1. Variable

2. Constant

3. Basic program Structure and statement

Pl/sql can reside in both Oracle database servers and Oracle development tools environments. In both environments, the Pl/sql engine accepts any pl/sql block and subroutine as input, and the engine executes a procedure statement that sends the SQL statement to the SQL statement executor executed by the Oracle server.

1, Pl/sql variable

(1) The declaration of the variable:

Variables are usually defined in the Declarations section of a pl/sql block, and each variable has a specific type.

The basic format for a variable definition is:

< variable name > < data type >[(width):=< initial value

For example, define a number type variable named Countnum, with an initial value of 1, which can be written as follows:

Countnum number: = 1;

--The basic naming rules for variables are as follows:

--a. Variable names must begin with a letter

--b. Variable length not exceeding 30 characters

--c. Cannot have spaces in variable names

(2) The properties of the variable

% is used to represent property prompts.

%type property. The%type property provides properties for variables and database columns. This property is very convenient, assuming that there is a table A, there is a field B, now to define a variable C, it needs its data type and field B, this time we can not know the data type of B, the direct use of b%type can be, such as: C B%type.

%rowtype property. This property provides a data type that represents one row of records in a table. With it, we can easily use a variable to represent a row in a cursor, such as Cursorrecord Cursorname%rowtype, where Cursorrecord represents a variable name on one row of the cursor, Cursorname represents the name of the corresponding cursor, using% RowType can be taken to a row of record types, so that later in the data, you can directly use the

Fetch cursorname into Cursorrecord. Sample code:

DECLARE CURSOR modulecursor is
      
      
select * from T_module;  
      
      
Modulerecord Modulecursor%rowtype;  
      
      
Begin
      
      
  Open modulecursor;  
      
      
  Fetch modulecursor into Modulerecord;  
      
      
  While Modulecursor%found   
      
      
  loop  
      
      
    dbms_output.put_line (Modulerecord.name | | '**********************');  
      
      
    Fetch modulecursor into Modulerecord;  
      
      
  End Loop;  
      
      
  Close modulecursor;  
      
      
End