PL/SQL控制结构

--1.条件分支语句

--语法

IF condition THEN

statements

[ELSIF condition THEN

statements]

[ELSE 

    statements]

END IF;



--2.CASE

--语法

CASE selector

WHEN expression1 THEN sequence_of_statements1;

WHEN expression2 THEN sequence_of_statements2;

...

WHEN expressionN THEN sequence_of_statementsN;

[ELSE sequence_of_statementsN+1]

END CASE;



CASE

WHEN search_condition1 THEN sequence_of_statements1;

WHEN search_condition2 THEN sequence_of_statements2;

...

WHEN search_conditionN THEN sequence_of_statementsN;

[ELSE sequence_of_statementsN+1]

END CASE;



--3.循环

--基本循环

--语法

LOOP

    statements1;

    ...

    EXIT [WHEN condition];

END LOOP;



--DEMO

DECLARE

i INT:=1;

BEGIN

    LOOP

        INSERT INTO temp VALUSE(i);

        EXIT WHEN i=10;

        i:=i+1;

    END LOOP;

END;

/



--WHILE循环

--语法

WHILE condition LOOP

    statements1;

    statements2;

    ...

END LOOP;



--DEMO

DECLARE

    i INT:=1;

BEGIN

    WHILE i<=10 LOOP

        INSERT INTO temp VALUES(i);

        i:=i+1;

    END LOOP;

END;

/



--FOR循环

--语法

FOR counter IN [REVERSE]

    lower_bound..upper_bound LOOP

    statements1;

    statements2;

    ...

END LOOP;



--DEMO

BEGIN

    FOR i IN REVERSE 1..10 LOOP

        INSERT INTO temp VALUES(i);

    END LOOP;

END;

/



--嵌套循环和标号

--DEMO

DECLARE

    result INT;

BEGIN

    <<outer>>

    FOR i IN 1..100 LOOP

        <<inner>>

        FOR j IN 1..10 LOOP

            result:=i*j;

            EXIT outer WHEN result=100;

            EXIT WHEN result = 50;

            dbms_output.put_line('inner:'||result);

        END LOOP inner;

        dbms_output.put_line('outer:'||result);

    END LOOP outer;

    dbms_output.put_line('dbms_output.put_line:'||result);

END;

/

        

4.顺序控制语句

--GOTO

--语法

GOTO label_name;



--DEMO

DECLARE

    i INT:=1;

BEGIN

    LOOP

        INSERT INTO temp VALUES(i);

        IF i=9 THEN

            GOTO end_loop;

        END IF;

        i:=i+1;

    END LOOP;

    <<end_loop>>

    dbms_output.put_line('循环结束');

END;

/

    

--NULL

--DEMO

DECLARE

    v_sal emp.sal%TYPE;

    v_ename emp.ename%TYPE;

BEGIN

    SELECT ename,sal INTO v_ename,v_sal

    FROM emp

    WHERE empno=&eno;

    IF v_sal<3000 THEN

        UPDATE emp SET comm=sal*0.1 WHERE ename=v_ename;

    ELSE

        NULL;

    END IF;

END;

/