在PL/SQL中使用布尔值 [英] Use of boolean in PL/SQL

问题描述

我在PL/SQL中有一个函数，该函数检查是否存在特定的emp_id:

I have a function in PL/SQL which checks if a particular emp_id exists or not which is:

CREATE OR REPLACE FUNCTION checkEmpNo(eno numeric)
RETURN boolean IS
    emp_number number;
BEGIN
    SELECT emp_id INTO emp_number
    FROM emp;
    IF eno=emp_number
    THEN
        return true;
    ELSE
        return false;
    END IF;
END checkEmpNo;

该函数编译成功，但是当我尝试以以下方式运行它时:

The function compiles successfully, but when I try to run it as:

DECLARE
    exist boolean;
BEGIN
    exist=checkEmpNo(1);
    dbms_output.put_line(exist);
END;

它返回错误:

ORA-06550: line 5, column 1:
PLS-00306: wrong number or types of arguments in call to 'PUT_LINE'
ORA-06550: line 5, column 1:
PL/SQL: Statement ignored

3. BEGIN
4. exist:=checkEmpNo(1);
5. dbms_output.put_line(exist);
6. END;

我也尝试过:

DECLARE
    exist boolean:=true;
BEGIN
    if(exist=checkEmpNo(1))
    then
        dbms_output.put_line('true');
    else
        dbms_output.put_line('false');
    end if;
END;

它返回错误:ORA-01422: exact fetch returns more than requested number of rows

推荐答案

dbms_output.put_line不会重载以接受布尔参数.您可以做类似的事情

dbms_output.put_line is not overloaded to accept a boolean argument. You can do something like

dbms_output.put_line( case when exist = true 
                           then 'true'
                           else 'false'
                        end );

将布尔值转换为字符串，然后可以将其传递给dbms_output.

to convert the boolean into a string that you can then pass to dbms_output.

ORA-01422错误是一个完全独立的问题.函数checkEmpNo包含SELECT INTO语句

The ORA-01422 error is a completely separate issue. The function checkEmpNo includes the SELECT INTO statement

SELECT emp_id 
  INTO emp_number
  FROM emp;

如果查询返回除1行以外的任何内容，则SELECT INTO将生成错误.在这种情况下，如果emp表中有多行，则会出现错误.我的猜测是，您希望函数执行类似的操作

A SELECT INTO will generate an error if the query returns anything other than 1 row. In this case, if there are multiple rows in the emp table, you'll get an error. My guess is that you would want your function to do something like

CREATE OR REPLACE FUNCTION checkEmpNo(p_eno number)
  RETURN boolean 
IS
  l_count number;
BEGIN
  SELECT count(*)
    INTO l_count
    FROM emp
   WHERE emp_id = p_eno;

  IF( l_count = 0 )
  THEN
    RETURN false;
  ELSE
    RETURN true;
  END IF;
END checkEmpNo;

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