PL/SQL syntax

1. Branching structure

In PL/SQL, the IF keyword is used as the starting segment of the program for the point structure.

There are several branching structures in general:

1) If Condition then statement end if;

2) If Condition then statement

Else then statement

End If;

3) If Condition then statement

elsif condition Then statement

...

Else then statement

End If;

The structure corresponding to the if () {},if () {}else () {},if () {}else if () {}...else{} in other languages

In addition, PL/SQL also provides the case keyword as an identifying segment of the branching structure.

There are several ways to use case:

1) Single-value matching for a field

Case Column1

When value1 then statement

When value2 then statement

...

End case;

This structure is similar to the switch structure in other languages.

2) Use case: When structure to express if: else conditional syntax

Case

When condition then statement

When condition then statement

...

End case;

2. Cyclic structure

In PL/SQL, the specific loop structure has the following types:

1) for

For i in Rs.first. Rs.last Loop

end Loop;

This structure is concise and efficient when traversing the collection that the cursor points to, which enables the automatic management of cursors: including cursors open, close, and auto Fetch.

Example:

Declare

cursor C_emp is

select * from EMP;

Emp_record Emp%rowtype;

begin

For Emp_record in C_emp

Loop

Dbms_output.put_line (emp_record.empno);

end Loop;

end;

This PL/SQL program does not open a cursor, does not use a FETCH statement, and does not close the cursor, but uses the for. The in structure automates these tasks automatically, so it is simple, efficient and error-prone.

2) Loop when

Loop

exit when (statement)

end Loop;

3) Loop while

While (statement)

Loop

end Loop;

4) Goto

Loop

if (statement) then goto label_name

End If;

end Loop;

<<label_name>>

In PL/SQL, you can use the form <<label_name>> to define a label that uses the GOTO keyword to jump to the label as it executes, thus ending the loop body.

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PL/SQL syntax