PL/SQL控制结构
順序結構
按先后順序
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分支判斷結構
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IF語句
IF condition THEN
statements;
[ELSIF condition?THEN
statements;]
[ELSE
statements;]
END IF;
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例：
DECLARE
v_myage number :=31;
BEGIN
IF v_myage<11
THEN
DBMS_OUTPUT.PUT_LINE(' I am a child ');
ELSIF v_myage<20 THEN
DBMS_OUTPUT.PUT_LINE(' I am young');
ELSIF v_myage<30 THEN
DBMS_OUTPUT.PUT_LINE('I am in twenties');
ELSIF v_myage<40 THEN
DBMS_OUTPUT.PUT_LINE(' I am in thirties');
ELSE
DBMS_OUT.PUT_LINE(' I am always yound');
END IF;
END;
/
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例：
DECLARE
v_myage number;
BEGIN
IF v_myage <11 THEN
DBMS_OUTPUT.PUT_LINE(' I am a child ');
ELSE
DBMS_OUTPUT.PUT_LINE(' I am not a child');
END IF;
END;
/
注：初始化不賦值默認為NULL，不能確定其數值。
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CASE表達式
CASE selector
WHEN expression1 THEN result1
WHEN expression2 THEN result2
...
WHEN expressionN THEN resultN
END;
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例：
SET VERIFY OFF
DECLARE
v_grade CHAR(1) := UPPER('&grade');
v_appraisal VARCHAR2(20);
BEGIN
v_appraisal := CASE v_grade
WHEN 'A' THEN??'Excllent'
WHEN 'B' THEN ' Very Good'
WHEN 'C' THEN 'GOOD'
ELSE 'No such grade'
END;
DBMS_OUTPUT.PUT_LIND('Grade: ' || v_grade || 'Appraisal ' || v_appraisal);
END;
/
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CASE語句
例:
DECARE
v_deptid NUMBER;
v_deptname VARCHAR2(20);
v_emps NUMBER;
v_mngid NUMBER := 108;
BEGIN
CASE v_mngid
WHEN??108 THEN
SELECT department_id,department_name
INTO v_deptid,v_deptname FROM departments
WHERE manager_id=108;
SELECT cout(*) INTO v_emps FROMemployees
WHERE department_id=v_deptid;
WHEN 200 THEN
END CASE;
DBMS_OUTPUT.PUT_LINE('You are working in the ' || v_deptname ||
'department. There are ' || v_emps || 'employees in this departmen');
END;
/
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NULL邏輯運算
FALSE AND NULL = FALSE
FALSE OR NULL = NULL
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短路
兩種條件中只要判斷一個條件成立則執行下一步
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IF condtion1 AND condition2
THEN
statements;
ELSE
statements;
END IF;
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IF condition1 OR condition2
THEN
statements;
ELSE
statements;
END IF;
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GOTO語句
GOTO??label_name;
GOTO語句用作無條件跳轉，但只能在pl/sql塊內部跳轉，需要與標簽連用，但是標簽后不能直接跟END，如果沒有表達式則加多一行NULL;
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例：
?DECLARE
…
BEGIN
IF condition THEN GOTO lastpoint END IF;
…
<<lastpoint>>
NULL;
END;
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例：
BEGIN
GOTO second_output;
DBMS_OUTPUT.PUT_LINE('The line will never execute.');
<<second_output>>
DBMS_OUT.PUT_LINE('We are here!');
END;
/
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循環結構
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Basic loop(基本循環)至少被執行一次
LOOP
statement1;
EXIT [WHEN condition];(退出循環)
END;
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例：
DECLARE
v_countryid loactions.country_id%TYPE := 'CA';
v_loc_id locations.location_id%TYPE;
v_counter NUMBER(2) :=1;
v_new_city locations.city%TYPE := 'Montreal';
BEGIN
SELECT MAX(location_id) INTO v_loc_id FROM locations
WHERE contry_id = v_countryid;
LOOP
INSERT INTO locatinos(location_id,city,country_id)
VALUES ((v_loc_id + v_counter),v_new_city,v_countryid);
v_counter := v_counter+1;
EXIT WHEN v_counter>3;
END LOOP;
END;
/
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FOR loop (FOR循環)
FOR counter IN [ REVERSE]
lower_bound..upper_bound LOOP
statement1;
statement2;
..
END LOOP;
注釋：counter?不需要定義，在END LOOP后就不能再被使用
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例：
DECLARE
v_coutryid locations.country_id%TYPE := 'CA';
v_loc_id locations.location_id%TYPE;
v_new_city locations.city%TYPE := 'Montreal';
BEGIN
SELECT MAX(location_id) INTO v_loc_id
FROM locations
WHERE country_id = v_countryid;
FOR i IN 1..3 LOOP
INSERT INTO locations(location_id,city,country_id)
VALUES((v_loc_id + i), v_new_city,v_countryid);
END LOOP;
END;
/
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WHILE loop(WHILE循環)
WHILE condition LOOP
statement1;
statement2;
END LOOP;
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例：
DECLARE
v_contryid locations.country_id%TYPE := 'CA';
v_loc_id locations.location_id%TYPE;
v_new_city locations.city%TPYE := 'Montreal';
v_counter NUMBER :=1;
BEGIN
SELECT MAX(location_id) INTO v_loc_id FROM locations
WHERE country_id = v_contryid;
WHILE v_counter <= 3 LOOP
INSERT INTO locations(location_id,city,country_id)
VALUES((v_loc_id + v_counter),v_new_city,v_countryid);
v_counter := v_counter +1;
END LOOP;
END;
/
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例：多重循環
…
BEGIN
<<Outer_loop>>
LOOP
v_counter :=??v_counter+1;
EXIT WHEN v_counter>10;
<< Inner_loop>>
LOOP
…
EXIT Outer_loop WHEN total_done = 'YES';
--Leave both loops
EXIT WHEN inner_done = 'Yes';
--Leave inner loop only
…
END LOOP inner_loop;
…
END LOOP Outer_loop;
END;
/
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CONTINUE語句
例：
DECLARE
v_total SIMPLE_TINTEGER :=0;
BEGIN
FOR i IN 1..10 LOOP
v_total := v_total +1;
DBMS_OUTPUT.PUT_LINE('Total is: ' || v_total);
CONTINUE WHEN i>5;
v_totail := v_total + I;
DBMS_OUTPUT.PUT_LINE('out of Loop Total is: ' || v_total);
END LOOP;
END;
/
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例：使用標簽跳轉到外層循環
DECLARE
v_total NUMBER :=0;
BEGIN
<<BeforeTopLoop>>
FOR i IN 1..10 LOOP
v_total := v_total +1;
DBMS_OUTPUT.PUT_LINE('Total is: ' || v_total);
FOR j IN 1..10 LOOP
CONTINUE BeforeTopLoop WHEN i+j>5;
v_total :=v_total +1;
END LOOP;
END LOOP;
END two_loop;
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程序員的基礎教程：菜鳥程序員
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