今天为了解决一个查询结果想两次遍历的方法,去ORACLE官网文档中心 https://docs.oracle.com/en/database/oracle/,意外发现这个有意思的for语句。还是官方资料给力啊
遍历一个游标
DECLARE CURSOR c1 IS SELECT last_name, job_id FROM employees WHERE job_id LIKE ‘%CLERK%‘ AND manager_id > 120 ORDER BY last_name; BEGIN FOR item IN c1 LOOP DBMS_OUTPUT.PUT_LINE (‘Name = ‘ || item.last_name || ‘, Job = ‘ || item.job_id); END LOOP; END; /
遍历一个子查询
BEGIN FOR item IN ( SELECT first_name || ‘ ‘ || last_name AS full_name, salary * 10 AS dream_salary FROM employees WHERE ROWNUM <= 5 ORDER BY dream_salary DESC, last_name ASC ) LOOP DBMS_OUTPUT.PUT_LINE (item.full_name || ‘ dreams of making ‘ || item.dream_salary); END LOOP; END; /
遍历列的列表
DECLARE TYPE empcurtyp IS REF CURSOR; TYPE namelist IS TABLE OF employees.last_name%TYPE; TYPE sallist IS TABLE OF employees.salary%TYPE; emp_cv empcurtyp; names namelist; sals sallist; BEGIN OPEN emp_cv FOR SELECT last_name, salary FROM employees WHERE job_id = ‘SA_REP‘ ORDER BY salary DESC; FETCH emp_cv BULK COLLECT INTO names, sals; CLOSE emp_cv; -- loop through the names and sals collections FOR i IN names.FIRST .. names.LAST LOOP DBMS_OUTPUT.PUT_LINE (‘Name = ‘ || names(i) || ‘, salary = ‘ || sals(i)); END LOOP; END; /
FOR循环使用关键字REVERSE倒着来
BEGIN DBMS_OUTPUT.PUT_LINE (‘upper_bound > lower_bound‘); FOR i IN REVERSE 1..3 LOOP DBMS_OUTPUT.PUT_LINE (i); END LOOP; DBMS_OUTPUT.PUT_LINE (‘upper_bound = lower_bound‘); FOR i IN REVERSE 2..2 LOOP DBMS_OUTPUT.PUT_LINE (i); END LOOP; DBMS_OUTPUT.PUT_LINE (‘upper_bound < lower_bound‘); FOR i IN REVERSE 3..1 LOOP DBMS_OUTPUT.PUT_LINE (i); END LOOP; END; /
更有意思的游标里可以包含游标对象
DECLARE TYPE emp_cur_typ IS REF CURSOR; emp_cur emp_cur_typ; dept_name departments.department_name%TYPE; emp_name employees.last_name%TYPE; CURSOR c1 IS SELECT department_name, CURSOR ( SELECT e.last_name FROM employees e WHERE e.department_id = d.department_id ORDER BY e.last_name ) employees FROM departments d WHERE department_name LIKE ‘A%‘ ORDER BY department_name; BEGIN OPEN c1; LOOP -- Process each row of query result set FETCH c1 INTO dept_name, emp_cur; EXIT WHEN c1%NOTFOUND; DBMS_OUTPUT.PUT_LINE(‘Department: ‘ || dept_name); LOOP -- Process each row of subquery result set FETCH emp_cur INTO emp_name; EXIT WHEN emp_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE(‘-- Employee: ‘ || emp_name); END LOOP; END LOOP; CLOSE c1; END; /
Exit还可以这样用
DECLARE s PLS_INTEGER := 0; i PLS_INTEGER := 0; j PLS_INTEGER; BEGIN <<outer_loop>> LOOP i := i + 1; j := 0; <<inner_loop>> LOOP j := j + 1; s := s + i * j; -- Sum several products EXIT inner_loop WHEN (j > 5); EXIT outer_loop WHEN ((i * j) > 15); END LOOP inner_loop; END LOOP outer_loop; DBMS_OUTPUT.PUT_LINE (‘The sum of products equals: ‘ || TO_CHAR(s)); END; /
continue也可以使用when
DECLARE x NUMBER := 0; BEGIN LOOP -- After CONTINUE statement, control resumes here DBMS_OUTPUT.PUT_LINE (‘Inside loop: x = ‘ || TO_CHAR(x)); x := x + 1; CONTINUE WHEN x < 3; DBMS_OUTPUT.PUT_LINE (‘Inside loop, after CONTINUE: x = ‘ || TO_CHAR(x)); EXIT WHEN x = 5; END LOOP; DBMS_OUTPUT.PUT_LINE (‘ After loop: x = ‘ || TO_CHAR(x)); END; /
FOR循环中变量可以重名
BEGIN <<outer_loop>> FOR i IN 1..3 LOOP <<inner_loop>> FOR i IN 1..3 LOOP IF outer_loop.i = 2 THEN DBMS_OUTPUT.PUT_LINE (‘outer: ‘ || TO_CHAR(outer_loop.i) || ‘ inner: ‘ || TO_CHAR(inner_loop.i)); END IF; END LOOP inner_loop; END LOOP outer_loop; END; /
跳转语句GOTO的使用
DECLARE p VARCHAR2(30); n PLS_INTEGER := 37; BEGIN FOR j in 2..ROUND(SQRT(n)) LOOP IF n MOD j = 0 THEN p := ‘ is not a prime number‘; GOTO print_now; END IF; END LOOP; p := ‘ is a prime number‘; <<print_now>> DBMS_OUTPUT.PUT_LINE(TO_CHAR(n) || p); END; /
DECLARE v_last_name VARCHAR2(25); v_emp_id NUMBER(6) := 120; BEGIN <<get_name>> SELECT last_name INTO v_last_name FROM employees WHERE employee_id = v_emp_id; BEGIN DBMS_OUTPUT.PUT_LINE (v_last_name); v_emp_id := v_emp_id + 5; IF v_emp_id < 120 THEN GOTO get_name; END IF; END; END; /
两次遍历一个结果的最终解法???
declare cursor c1 is select stockInfo from T_stock ORDER BY id; BEGIN FOR item IN c1 LOOP DBMS_OUTPUT.PUT_LINE (‘首次输出 = ‘ || item.stockInfo); END LOOP; FOR item IN c1 LOOP DBMS_OUTPUT.PUT_LINE (‘二次访问 = ‘ || item.stockInfo); END LOOP; END;
原文:https://www.cnblogs.com/sdlz/p/15354039.html