刚打开游标的时候，是位于一个空行，要用fetch into 才能到第一行。
只是要注意用更新游标的时候，不能在游标期间commit. 否则会报ORA-01002: fetch out of sequence就是COMMIT导致的错误。在打开有for update的cursor时，系统会给取出的数据加上排他锁(exclusive), 这样在这个锁释放前其他用户不能对这些记录作update、delete和加锁。而我一旦执行了commit,锁就释放了，游标也变成无效的,再去fetch数据时就出现错误了。因而要把commit放在循环外，等到所有数据处理完成后再commit,然后关闭cursor隐含游标--------又名SQL游标，用于处理单行select into 和 DML语句。SQL%ISOPENSQL%FOUNDSQL%NOTFOUNDSQL%ROWCOUNT显示游标
--------用户处理select语句返回的多行数据。select语句返回多行数据处理方式：[1]显示游标；[2]select ... bulk collect into 集合变量...；【1】显示游标属性[1] %ISOPEN 检测游标是否打开。[2] %FOUND 检测游标结果集是否存在数据。[3] %NOTFOUND 是否不存在数据。[4] %ROWCOUNT 游标已提取的实际行数【2】使用显示游标[1] 定义游标CURSOR cursor_name IS select_statement;[2] 打开游标OPEN cursor_name;[3] 提取数据FECTH cursor_name INTO variable,...[4] 关闭数据CLOSE cursor_name;使用标量变量：DECLARECursor emp_cur IS select ename,sal from emp order by empno;v_ename emp.ename%TYPE;v_sal emp.sal%TYPE;BEGINIF NOT emp_cur%ISOPEN THEN OPEN emp_cur; DBMS_OUTPUT.PUT_LINE('打开游标');END IF;NULL;LOOP FETCH emp_cur INTO v_ename,v_sal; EXIT WHEN emp_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE('用户名：'||v_ename||'，工资：'||v_sal);END LOOP;NULL;IF emp_cur%ISOPEN THEN CLOSE emp_cur; DBMS_OUTPUT.PUT_LINE('关闭游标');END IF;END; 使用PLSQL记录变量：
DECLARECursor emp_cur IS select ename,sal from emp order by empno;emp_record emp_cur%ROWTYPE;BEGINIF NOT emp_cur%ISOPEN THEN OPEN emp_cur; DBMS_OUTPUT.PUT_LINE('打开游标');END IF;NULL;LOOP FETCH emp_cur INTO emp_record; EXIT WHEN emp_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE('用户名：'||emp_record.ename||'，工资：'||emp_record.sal);END LOOP;NULL;IF emp_cur%ISOPEN THEN CLOSE emp_cur; DBMS_OUTPUT.PUT_LINE('关闭游标');END IF;END; 使用PLSQL集合变量：
DECLARECursor emp_cur IS select ename,sal from emp order by empno;TYPE emp_table_type IS TABLE OF emp_cur%ROWTYPE INDEX BY BINARY_INTEGER;emp_table emp_table_type;i number;BEGINi := 1;IF NOT emp_cur%ISOPEN THEN OPEN emp_cur; DBMS_OUTPUT.PUT_LINE('打开游标');END IF;NULL;LOOP FETCH emp_cur INTO emp_table(i); EXIT WHEN emp_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE('用户名：'||emp_table(i).ename||'，工资：'||emp_table(i).sal); i := i + 1;END LOOP;NULL;IF emp_cur%ISOPEN THEN CLOSE emp_cur; DBMS_OUTPUT.PUT_LINE('关闭游标');END IF;END; 【3】循环游标
FOR record_name IN cursor_name|select_statement LOOP statement; ....END LOOP;declare cursor emp_cusor is select ename,sal from emp where deptno = &no order by empno;beginfor emp_record in emp_cusor loop dbms_output.put_line('姓名：'||emp_record.ename||'，工资：'||emp_record.sal);end loop;end;beginfor emp_record in (select ename,sal from scott.emp where deptno = &no order by empno) loop dbms_output.put_line('姓名：'||emp_record.ename||'，工资：'||emp_record.sal);end loop;end; 【4】参数游标
CURSOR cursor_name(parameter_name datatype) IS select_statement; --只能制定类型，不能指定具体大小OPEN cursor_name(参数值);FECTH cursor_name INTO variable,...;CLOSE cursor_name;declare cursor emp_cursor(v_depnto number) is select ename,sal from scott.emp where deptno = v_depnto order by empno;emp_record emp_cursor%rowtype;v_dno number;beginv_dno := &no;if not emp_cursor%isopen then open emp_cursor(v_dno);end if; null;loop fetch emp_cursor into emp_record; exit when emp_cursor%notfound; dbms_output.put_line('姓名：'||emp_record.ename||'，工资：'||emp_record.sal);end loop;null;if emp_cursor%isopen then close emp_cursor;end if;end; declare cursor emp_cursor(v_depnto number) is select ename,sal from scott.emp where deptno = v_depnto order by empno;v_dno number;beginv_dno := &no;for emp_record in emp_cursor(v_dno) loop dbms_output.put_line('姓名：'||emp_record.ename||'，工资：'||emp_record.sal);end loop;end; 【5】更新、删除游标行
CURSOR cursor_name IS select_statementFOR UPDATE [OF column_reference] [NOWAITE]; -- OF子句指定对特定表加锁。UPDATE table_name SET column=.. WHERE CURRENT OF cursor_name;DELETE table_name WHERE CURRENT OF cursor_name;declare cursor test_cursor is select empno,ename,sal,deptno from scott.test for update; test_record test_cursor%rowtype; v_deptno number; v_sal test.sal%type;begin v_deptno := &no; if not test_cursor%isopen then open test_cursor; end if; loop fetch test_cursor into test_record; exit when test_cursor%notfound; dbms_output.put_line('姓名：'||test_record.ename||'，旧工资：'||test_record.sal); if test_record.deptno = v_deptno then update scott.test set sal=2*sal where current of test_cursor; else update scott.test set sal=3*sal where current of test_cursor; end if; end loop; close test_cursor;end; declarecursor test_cursor is select empno,ename,sal,deptno from scott.test for update; v_deptno NUMBER:=&dno;beginfor test_record in test_cursor loop if test_record.deptno = v_deptno then dbms_output.put_line('姓名：'||test_record.ename||'，旧工资：'||test_record.sal); update scott.test set sal = sal*1.5 where current of test_cursor; end if; end loop;end; 使用游标删除数据
declare cursor test_cursor(v_deptno number) is select deptno,empno,ename,comm from scott.test where deptno = v_deptno for update;v_dno test.deptno%type := &dno;begin for test_record in test_cursor(v_dno) loop if test_record.comm is null then dbms_output.put_line('用户名：'||test_record.ename||'部门：'||test_record.deptno); delete from scott.test where current of test_cursor; end if; end loop; end; 【6】游标变量
指向内存地址的指针。可以在打开游标时指定其所对应的SELECT语句，实现动态游标。[1]定义REF CURSOR类型和游标变量：Type ref_type_name IS REF CURSOR [RETURN return_type --必须是PL/SQL记录类型]; 说明：如果指定RETURN子句，那么在打开游标时SELECT语句的返回结果必须与RETURN子句所指定的记录类型匹配。cursor_variable ref_type_name;SYS_REFCURSOR[2]打开游标，指定对应的SELECT语句：OPEN cursor_variable FOR select_statement;[3]提取数据FETCH cursor_variable INTO variable1,variable,...;[4]关闭游标CLOSE cursor_variable;不使用RETURN子句----------------DECLARETYPE ref_type_table IS REF CURSOR;v_cursor ref_type_table;emp_record emp%rowtype;BEGIN OPEN v_cursor FOR select * from emp where deptno=&no; LOOP FETCH v_cursor INTO emp_record; EXIT WHEN v_cursor%NOTFOUND; dbms_output.put_line('员工号：'||emp_record.ename||'部门号：'||emp_record.deptno); END LOOP; CLOSE v_cursor;END; 使用RETURN子句
--------------DECLAREemp_record emp%rowtype;TYPE ref_type_table IS REF CURSOR RETURN emp%rowtype;v_cursor ref_type_table;BEGIN OPEN v_cursor FOR select * from emp where deptno=&no; LOOP FETCH v_cursor INTO emp_record; EXIT WHEN v_cursor%NOTFOUND; dbms_output.put_line('员工号：'||emp_record.ename||'部门号：'||emp_record.deptno); END LOOP; CLOSE v_cursor;END;DECLAREType emp_record_type IS RECORD( ename emp.ename%TYPE, salary emp.sal%TYPE, deptno emp.deptno%TYPE);emp_record emp_record_type;TYPE ref_type_table IS REF CURSOR RETURN emp_record_type;v_cursor ref_type_table;BEGIN OPEN v_cursor FOR select ename,sal,deptno from emp where deptno=&no; LOOP FETCH v_cursor INTO emp_record; EXIT WHEN v_cursor%NOTFOUND; dbms_output.put_line('员工号：'||emp_record.ename||'，部门号：'||emp_record.deptno||'，工资：'||emp_record.salary); END LOOP; CLOSE v_cursor;END; 【7】使用游标批量获取
FETCH ... BULK COLLECT INTO ...[LIMIT row_number];不限制行数
----------DECLARE CURSOR emp_cursor(v_deptno number) IS SELECT * FROM EMP WHERE deptno = v_deptno; TYPE type_emp_table IS TABLE OF emp%ROWTYPE INDEX BY BINARY_INTEGER; emp_table type_emp_table; v_dno emp.deptno%TYPE;BEGIN v_dno := &no; OPEN emp_cursor(v_dno); FETCH emp_cursor BULK COLLECT INTO emp_table; CLOSE emp_cursor; FOR i IN 1..emp_table.COUNT LOOP dbms_output.put_line('员工号：'||emp_table(i).ename||'工资：'||emp_table(i).sal); END LOOP; CLOSE emp_cursor;END; 限制行数
--------DECLARE CURSOR emp_cursor(v_deptno number) IS SELECT * FROM EMP WHERE deptno = v_deptno; TYPE type_emp_table IS TABLE OF emp%ROWTYPE INDEX BY BINARY_INTEGER; emp_table type_emp_table; v_dno emp.deptno%TYPE;BEGIN v_dno := &no; OPEN emp_cursor(v_dno); FETCH emp_cursor BULK COLLECT INTO emp_table LIMIT &2; CLOSE emp_cursor; FOR i IN 1..emp_table.COUNT LOOP dbms_output.put_line('员工号：'||emp_table(i).ename||'工资：'||emp_table(i).sal); END LOOP; CLOSE emp_cursor;END; 【8】使用CURSOR表达式
作用嵌套游标。DECLARE CURSOR dept_emp_cursor(v_deptno number) IS SELECT dname,cursor(SELECT * FROM emp e WHERE e.deptno = d.deptno) FROM dept d WHERE deptno = v_deptno; TYPE emp_cursor_type IS REF CURSOR; emp_cursor emp_cursor_type; emp_record emp%ROWTYPE; v_name dept.dname%TYPE; v_dno emp.deptno%TYPE;BEGIN v_dno := &no; OPEN dept_emp_cursor(v_dno); loop FETCH dept_emp_cursor INTO v_name,emp_cursor; EXIT WHEN dept_emp_cursor%NOTFOUND; dbms_output.put_line('部门名称：'||v_name); LOOP FETCH emp_cursor INTO emp_record; EXIT WHEN emp_cursor%NOTFOUND; dbms_output.put_line('员工名称：'||emp_record.ename||'，工资：'||emp_record.sal); END LOOP; end loop; CLOSE dept_emp_cursor;END;