Basic block format and syntax for PL/SQL Learning notes

One: PL/SQL program block

PL/SQL is a block-structured language, and a PL/SQL program is a code logic block.

The PL/SQL program consists of three components:

1	Declarations Section Starting with the keyword DECLARE , it is an optional part that declares all variables, cursors, subroutines, and other elements that are used in the program with the assigned initial value .
2	Executable Commands Section Use the keyword begin and end packages , must have. Defines a series of PL/SQL statements .
3	Exception Handling Section Use the keyword EXCEPTION, Optional, to handle exceptions captured by the executable commands section .

Two: Basic format

DECLARE    <declarations section>BEGIN   <executable command (s) >EXCEPTION   <exception Handling>END;

Three: Notes

Single-line comment: Use separators--。

Multiline Comments:/* and */.

Four: operational symbols

+, -, *, /	addition, subtraction/negation, multiplication, division
%	Property Index
‘	String
.	Dot operator
(,)	An expression or list separator
:	Host variable Indicator
,	Item Separator
"	Quoted identifier delimiter
=	Relational operators
@	Remote Access Indicator
;	Declaration Terminator, Statement Terminator
:=	Assignment operators
=	Operator Association
||	Connection operators, string connections
**	Exponentiation operator
<<, >>	Label delimiter (start and end)
/*, */	Multiline comment delimiter (start and end)
--	Single-line Comment indicator
..	Range operations
<, <=, >=	Relational operators
<>, ' =, ~=, ^=	Unequal operators

Five: Program unit

PL/SQL Program unit: A named PL/SQL block in a database that is stored as a database object in a database.

There are five main categories:

PL/SQL Block: A block of program code that carries out some action, including the three blocks mentioned above (where declarations, exceptions are optional).

Procedure: Performs a specific operation with no return value.

Function: A complex calculation with a return value.

Package: Logically related procedures and functions are organized together, analogous to classes in Java.

Trigger: Event trigger, perform the appropriate action.

Basic block format and syntax for PL/SQL Learning notes