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ORACLEPL/SQL基础部分

时间:2021-07-01 10:21:17 帮助过:18人阅读

declare /*定义SQL中使用的变量*/ v_cid number; v_cname varchar2(10); v_count number; begin select cid,cname into v_cid,v_cname from classes where cid=2; if(v_cname='9999') then select count(cname) into v_count from classes where cname='9999

declare
/*定义SQL中使用的变量*/
v_cid number;
v_cname varchar2(10);
v_count number;
begin
select cid,cname into v_cid,v_cname from classes where cid=2;
if(v_cname='9999') then
select count(cname) into v_count from classes where cname='9999';
dbms_output.put_line('cname为9999的记录为:' || v_count);
end if;
end;
/


declare
/*定义SQL中使用的变量*/
v_cid number;
v_cname varchar2(10);
v_count number;
begin
v_cid:=8;
select cid,cname into v_cid,v_cname from classes where cid=v_cid;
if(v_cname='9999') then
select count(cname) into v_count from classes where cname='9999';
dbms_output.put_line('cname为9999的记录为:' || v_count);
end if;
exception
when no_data_found then
dbms_output.put_line('数据不存在');
end;
/

--定义一个只包含执行部分和结束部分的PL/SQL块
begin
Dbms_Output.put_line('Hello World');
end;
/

--定义包含子块的PL/SQL块
declare
v_cid number;
v_cname varchar2(10);
v_count number;
begin
begin
v_cid:=2;
select cname into v_cname from classes where cid=v_cid;
dbms_output.put_line('子块中查出来cid=2的cname:'||v_cname);
end;
select cname into v_cname from classes where cid=3;
dbms_output.put_line('外层查询出来cid=3的cname:'||v_cname);
end;
/

---------------------------------------------------------
--使用参考类型定义-变量类型(%type)
declare
v_all varchar(10);
v_cid number;
v_cname v_all%type; --使用参考类型定义-变量类型
v_count number;
begin
begin
v_cid:=2;
select cname into v_cname from classes where cid=v_cid;
dbms_output.put_line('子块中查出来cid=2的cname:'||v_cname);
end;
select cname into v_cname from classes where cid=3;
dbms_output.put_line('外层查询出来cid=3的cname:'||v_cname);
end;
/


declare
v_cid number;
v_cname classes.cname%type; --使用参考类型定义变量类型
v_count number;
begin
begin
v_cid:=2;
select cname into v_cname from classes where cid=v_cid;
dbms_output.put_line('子块中查出来cid=2的cname:'||v_cname);
end;
select cname into v_cname from classes where cid=3;
dbms_output.put_line('外层查询出来cid=3的cname:'||v_cname);
end;
/

--使用参考类型定义-变量类型(%rowtype)
declare
v_cid number;
v_classes classes%rowtype; -- v_classes:变量名称;classes表名
v_count number;
begin
begin
select cname into v_classes.cname from classes where cid=2;
dbms_output.put_line('子块中查出来cid=2的cname:'||v_classes.cname);
end;
select cname into v_classes.cname from classes where cid=3;
dbms_output.put_line('外层查询出来cid=3的cname:'||v_classes.cname);
end;
/

declare
c_cid constant number:=3; --声明常量,必须初始化赋值否则会报错。
v_classes classes%rowtype;
v_count number not null :=1; --声明not null变量,必须也为初始化赋值
begin
select cname into v_classes.cname from classes where cid=c_cid;
dbms_output.put_line('外层查询出来cid=3的cname:'||v_classes.cname);
end;
/

declare
cid number :=2; --定义PL/SQL变量时不要跟数据库字段列名相同,否则会很麻烦,比如
begin
delete from studentinfo where cid=cid;
end;
/

--之前studentInfo数据:
SQL> select * from studentinfo;
STUID SNAME CID ADDRESS
--------------------------------------- ---------- --------------------------------------- --------------------
2 zhangsan 1 hnzz
3 lisi 1 hncs
4 wangwu 2 hncd
5 zhaoliu 2 hndd
6 zhudao 3 hnyy
7 david 3 hnyy
6 rows selected

SQL> declare
2 cid number :=2;
3 begin
4 delete from studentinfo where cid=cid;
5 end;
6 /
PL/SQL procedure successfully completed

SQL> select * from studentinfo;
STUID SNAME CID ADDRESS
--------------------------------------- ---------- --------------------------------------- --------------------

SQL>
--以上调用删除的不是单行数据,而是整个数据表。

--IF THEN 单分支语句;
declare
v_cname varchar2(10);
begin
select cname into v_cname from classes where cid=2;
if(v_cname='9999') then
dbms_output.put_line('cid=2的记录cname为:'||v_cname);
end if;
end;
/

--双分支语句;
declare
v_cname varchar2(10);
begin
select cname into v_cname from classes where cid=3;
if(v_cname='9999') then
dbms_output.put_line('cid=2的记录cname为:'||v_cname);
else
dbms_output.put_line('执行的是else里面程序'||v_cname);
end if;
end;
/

--多条分支语句 if ...then ..elsif...then...else
declare
v_cname varchar2(10);
begin
select cname into v_cname from classes where cid=1;
if(v_cname='9999') then
dbms_output.put_line('v_cname=9999打印了。值为:'||v_cname);
elsif(v_cname='0901') then
dbms_output.put_line('v_cname=0901打印了。值为:'||v_cname);
elsif(v_cname='0903') then
dbms_output.put_line('v_cname=0903打印了。值为:'||v_cname);
else
dbms_output.put_line('没有任何值可打...'||v_cname);
end if;
end;

--CASE语句
declare
v_test varchar(1):='f';
begin
case v_test
when 'A' then dbms_output.put_line('输出了A');
when 'B' then dbms_output.put_line('输出了B');
when 'C' then dbms_output.put_line('输出了C');
else dbms_output.put_line('输出了X');
end case;
end;


declare
v_cname classes.cname%type;
begin
select cname into v_cname from classes where cid=2;
case
when v_cname='9999' then
dbms_output.put_line('执行了1');
when v_cname='0901' then
dbms_output.put_line('执行了2');
when v_cname='0903' then
dbms_output.put_line('执行了3');
else
dbms_output.put_line('执行了0');
end case;
end;
/

--循环结构
declare
i number:=1;
begin
loop
dbms_output.put_line(i || '的平方数为:' || i*i);
i:=i+1;
exit when i>5;
end loop;
end;
/

--使用loop循环向表中插入30条记录
declare
i number :=1;
begin
loop
insert into classes values(seq_stuid.nextval,'A');
i:=i+1;
exit when i>=30;
end loop;
end;
/

--使用loop循环&if条件判断语句向表中插入30条记录
declare
i number:=1;
begin
loop
insert into classes values(seq_stuid.nextval,'B');
i:=i+1;
if i>=30 then
exit;
end if;
end loop;
end;
/

--while循环
declare
i number :=1;
begin
while(i<=5) loop
dbms_output.put_line(i||'的平方和为:'||i*i);
i:=i+1;
end loop;
end;
/
--使用while循环向表中插入30条记录
declare
i number :=1;
begin
while i<=30 loop
insert into classes values(seq_stuid.nextval,'C');
i:=i+1;
end loop;
end;
/

--使用for循环
declare
i number :=1;
begin
for i in 1..30 loop --in 从小到大顺序遍历
insert into classes values(seq_stuid.nextval,'D');
end loop;
end;
/

--终止for循环
declare
i number :=1;
begin
for v_content in reverse 1..5 loop
insert into classes values(seq_stuid.nextval,'G');
if(v_content=3) then exit;
end if;
end loop;
end;
/

--GOTO语句
begin
<>
for i in reverse 1..3 loop
<>
for j in 1..3 loop
dbms_output.put_line('i='||i||','||'j='||j);
end loop;
end loop;
end;


--游标定义使用 查询一组数据
declare
cursor classes_cursor is select * from classes;
v_cid classes.cid%type;
v_cname classes.cname%type;
begin
if not classes_cursor%isopen then
open classes_cursor;
end if;
loop
fetch classes_cursor into v_cid,v_cname;
exit when classes_cursor%notfound;
dbms_output.put_line('第'||classes_cursor%rowcount ||'条记录'||'班级id:'||v_cid || '班级编号'||v_cname);
end loop;
close classes_cursor;
end;
/

--对于select定义的游标的每一列,fetch变量列表都应该有一个变量与之对应,而且变量的类型要相同,变量顺序也要一直。

declare
cursor classes_cursor is select * from classes;
v_classes classes%rowtype;
begin
if not classes_cursor%isopen then
open classes_cursor;
end if;
loop
fetch classes_cursor into v_classes;
exit when classes_cursor%notfound;
dbms_output.put_line('第'||classes_cursor%rowcount ||'条记录'||'班级id:'||v_classes.cid || '班级编号'||v_classes.cname);
end loop;
close classes_cursor;
end;
/
--以上使用%rowtype指定查询结果变量。

--以下使用有表名也可以定义%rowtype类型
declare
cursor classes_cursor is select * from classes;
v_classes classes_cursor%rowtype;
begin
if not classes_cursor%isopen then
open classes_cursor;
end if;
loop
fetch classes_cursor into v_classes;
exit when classes_cursor%notfound;
dbms_output.put_line('第'||classes_cursor%rowcount ||'条记录'||'班级id:'||v_classes.cid || '班级编号'||v_classes.cname);
end loop;
close classes_cursor;
end;
/

--使用while循环迭代游标处理结果集
declare
cursor class_cursor is select * from classes; --class_cursor:游标名,存放游标查询出来所有结果集数
v_classes class_cursor%rowtype; --v_classes:行变量,用于下面取值“.”列明
begin
if not class_cursor%isopen then
open class_cursor;
end if;
fetch class_cursor into v_classes; --和下面相同,因为while循环判断之前先拿到值进行判断是否有值才进行循环
while class_cursor%found loop
dbms_output.put_line('第'||class_cursor%rowcount ||'条记录'||'班级id:'||v_classes.cid || '班级编号'||v_classes.cname);
fetch class_cursor into v_classes; --和上面相同,这句意思逐一获取到值。
end loop;
close class_cursor;
end;
/
--使用for循环迭代,因为oracle数据库对使用for循环变量检索游标进行了简化,并隐式的定义了一个游标名 %rowtype类型的记录变量,
--把游标所有指向当前数据放入到该变量当中去。游标的打开、数据读取、游标关闭都有oracle数据库自动完成。也就是使用for循环不需要
--也不能使用open语句、fetch、close语句。
declare
cursor class_cursor is select * from classes;
begin
for v_classes in class_cursor loop
dbms_output.put_line('第'||class_cursor%rowcount ||'条记录'||'班级id:'||v_classes.cid || '班级编号'||v_classes.cname);
end loop;
end;

--使用子查询的for循环实现上面功能;
begin
for v_classes in (select * from classes) loop
dbms_output.put_line('班级id:'||v_classes.cid || '班级编号'||v_classes.cname);
end loop;
end;
/

--隐式游标,ORACLE数据库自动管理,又被成SQL游标
begin
update classes set cname='5555' where cid=100;
if SQL%NOTFOUND THEN
dbms_output.put_line('没有找到更新记录');
insert into classes values(100,'5555');
commit;
end if;
end;

begin
update classes set cname='6666' where cid=100;
if SQL%ROWCOUNT = 0 THEN
dbms_output.put_line('没有找到更新记录');
insert into classes values(100,'5555');
commit;
end if;
end;

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