PL/SQL 游标详解
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
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又名SQL游标,用于处理单行select into 和 DML语句。
SQL%ISOPEN
SQL%FOUND
SQL%NOTFOUND
SQL%ROWCOUNT
显示游标
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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:
DECLARE Cursor emp_cur IS select ename,sal from emp order by empno; v_ename emp.ename%TYPE; v_sal emp.sal%TYPE; BEGIN 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 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:
DECLARE Cursor emp_cur IS select ename,sal from emp order by empno; emp_record emp_cur%ROWTYPE; BEGIN 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_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:
DECLARE Cursor 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; BEGIN i := 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; begin for emp_record in emp_cusor loop dbms_output.put_line('姓名:'||emp_record.ename||',工资:'||emp_record.sal); end loop; end; begin for 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; begin v_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; begin v_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_statement
FOR 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; declare cursor test_cursor is select empno,ename,sal,deptno from scott.test for update; v_deptno NUMBER:=&dno; begin for 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
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DECLARE TYPE 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
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DECLARE emp_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; DECLARE Type 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
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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
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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;
posted on 2014-05-24 15:29 Sunny_NUAA 阅读(660) 评论(0) 编辑 收藏 举报