--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;
/