Oracle存储过程

-- 打印信息用的测试函数
DECLARE
    P1 NUMBER:=0;
BEGIN
    DBMS_OUTPUT.PUT_LINE(P1);
END;

-- 打印用的测试函数
DECLARE
    P1 NUMBER:=0;
BEGIN
    "ABCDE"(3,P1);
    DBMS_OUTPUT.PUT_LINE(P1);
END;

-- 简单的存储过程
CREATE OR REPLACE PROCEDURE ABCDE
(P1 IN VARCHAR,P2 OUT NUMBER)
AS BEGIN
  SELECT COUNT(0) INTO P2 FROM TABLE1;
END;

-- 游标和变量的简单应用
CREATE OR REPLACE PROCEDURE ABCDE
(P1 IN VARCHAR,P2 OUT NUMBER)
AS
/** 游标和变量的定义 **/
CURSOR CURSOR1 IS SELECT COUNT(0) FROM TABLE1;
C1 NUMBER;
BEGIN
OPEN CURSOR1;
FETCH CURSOR1 INTO P2;
CLOSE CURSOR1;
END;

/** FOR...循环遍历游标 **/
CREATE OR REPLACE
PROCEDURE ABCDE
(P1 IN VARCHAR,P2 OUT NUMBER)
AS
CURSOR CURSOR1 IS SELECT T_AGE FROM TABLE1;
BEGIN
P2:=0;
/** 感觉for循环是最适合遍历游标的，打开关闭游标都自动处理了 **/
FOR CS IN CURSOR1 LOOP
P2:=P2+CS.T_AGE;
END LOOP;
END;

/** DO...WHILE...循环遍历游标 **/
CREATE OR REPLACE
PROCEDURE ABCDE
(P1 IN VARCHAR,P2 OUT NUMBER)
AS
CURSOR CURSOR1 IS SELECT T_AGE FROM TABLE1;
C1 NUMBER;
BEGIN
P2:=0;
OPEN CURSOR1;

LOOP FETCH CURSOR1 INTO C1;
EXIT WHEN CURSOR1%NOTFOUND;
P2:=P2+C1;
END LOOP;

CLOSE CURSOR1;
END;


/** WHILE...循环遍历游标 **/
CREATE OR REPLACE
PROCEDURE ABCDE
(P1 IN VARCHAR,P2 OUT NUMBER)
AS
CURSOR CURSOR1 IS SELECT T_AGE FROM TABLE1;
C1 NUMBER;
BEGIN
P2:=0;
OPEN CURSOR1;

FETCH CURSOR1 INTO C1;
WHILE CURSOR1%FOUND LOOP
P2:=P2+C1;
FETCH CURSOR1 INTO C1;
END LOOP;

CLOSE CURSOR1;
END;


-- CURSOR1%ROWCOUNT的使用
CREATE OR REPLACE
PROCEDURE ABCDE
(P1 IN VARCHAR,P2 OUT NUMBER)
AS
CURSOR CURSOR1 IS SELECT T_AGE FROM TABLE1;
BEGIN
OPEN CURSOR1;
LOOP FETCH CURSOR1 INTO P2;
/**ROWCOUNT记录了游标的行数，此案例P2记录了每一次的行号，因此最后的结果是记录总条数**/
P2:=CURSOR1%ROWCOUNT;
EXIT WHEN CURSOR1%NOTFOUND;
END LOOP;
CLOSE CURSOR1;
END;


从游标中取值，%FOUND用于判断本次取值是否有值，进行%FOUND判断可以有效地避免no_data_found的问题；
FETCH直译为取，从游标取值的意思，在打开游标之后，在FETCH之前，%FOUND在程序中一直是false的状态，
要先FETCH，再%FOUND判断。

too_many_rows异常，不仅在存储过程中，在代码中也存在这个问题，需要考虑结果是数组还是一个对象，代码中通常只取第一个，
而游标因为是逐行取值，结合%FOUND判断可以完全避免此异常。


CREATE OR REPLACE
PROCEDURE ABCDE
(P2 OUT VARCHAR)
AS
CURSOR CURSOR1 IS SELECT T.T_AGE FROM(SELECT T_AGE,ROWNUM RNO FROM TABLE1) T WHERE RNO BETWEEN 0 AND 1;
C1 NUMBER;
BEGIN
P2:='';
OPEN CURSOR1;
IF CURSOR1%FOUND THEN P2:=P2||'FOUND; ';ELSE P2:=P2||'NOTFOUND; '; END IF;
FETCH CURSOR1 INTO C1;
IF CURSOR1%FOUND THEN P2:=P2||'FOUND; ';ELSE P2:=P2||'NOTFOUND; '; END IF;
FETCH CURSOR1 INTO C1;
IF CURSOR1%FOUND THEN P2:=P2||'FOUND; ';ELSE P2:=P2||'NOTFOUND; '; END IF;
CLOSE CURSOR1;
END;