Pl-sql Programming Basics (3)

Loop structure:

1, Loop loop structure

Grammar:

LOOP

The statement to execute;

Exit when < conditions >--Exits the loop if the condition is met

END LOOP;

Example: An integer that loops out 1-10

DECLARE  Number: = 1;   BEGIN      LOOP         dbms_output.put_line (v_num);         V_num:=+1;          EXIT  when Ten ;      END LOOP;      END;

The drawback of loop structure: The structure is not clear enough, exit easy to write.

2. While loop structure

Grammar:

While < Boolean expressions > LOOP

The statement to execute;

END LOOP;

Example: Displaying an integer of 1-10;

DECLARE  Number: = 1;   BEGIN      while <= Ten LOOP         Dbms_output.put_line (v_num);         V_num:=+1;      END LOOP;      END;

3. For loop

Grammar:

For loop counter in [REVERSE] offline ... Upper LOOP

The statement to execute;

END LOOP;

Example: Displaying an integer of 1-10

DECLARE  number; BEGIN   for inch 1.. Ten LOOP          Dbms_output. Put_Line (v_num);     END LOOP; END;

In the For loop, once per loop, the loop variable is automatically +1, using the keyword reverse, the loop variable automatically-1, the number following in reverse must be small to large, and must be an integer, cannot be a variable or an expression, you can use Exit to exit the loop.

In the previous example, if you add reverse, the output is descending.

Summarize:

The loop structure can perform certain operations repeatedly, taking precedence over a for loop in the known number of cycles, and using a while loop for unknown times. Exit can be nested in any loop, terminating the loop directly. Loop is not used in general!

Pl-sql Programming Basics (3)