PL/SQL 块查询 - 显示总计、最大值、最小值和平均值

Question

我是 PL/SQL 的新手，需要弄清楚以下问题。如果有人可以帮助我进行查询，我将不胜感激，以便我了解问题的构成。

我想创建一个新的匿名 PL/SQL 块，它将显示公司中的员工总数，他们的最高、最低和平均工资以及他们的平均工资四舍五入到整数。

这是正确的吗？

SELECT ROUND(MAX(salary),0) 'Maximum',  
ROUND(MIN(salary),0) 'Minimum',  
ROUND(SUM(salary),0) 'Sum',  
ROUND(AVG(salary),0) 'Average'  
FROM employees;  

PL/SQL 让我困惑

Answer 1

你有引号的问题：在列别名中，如果需要，你只能使用"，或者简单地定义不带引号的别名；区别在于，例如：

SQL> SELECT count(employee_id) as "Number of employees", -- double quotes: this alias will keep the case of my string and have spaces
  2  ROUND(MAX(salary),0) "Maximum",
  3  ROUND(MIN(salary),0) "Minimum",
  4  ROUND(SUM(salary),0) Sum, -- no quotes: this will be in UPPERCASE and you can have no spaces
  5  ROUND(AVG(salary),0) Average
  6  FROM employees;

Number of employees    Maximum    Minimum        SUM    AVERAGE
------------------- ---------- ---------- ---------- ----------
                107      24000       2100     691416       6462

此外，准确地说，这是一个 SQL 查询，而下面是一个 PL/SQL 块：

declare
    vCount number;
    vMax number;
    vMin number;
    vSum number;
    vAvg number;
begin  
    SELECT count(employee_id) as "Number of employees", 
    ROUND(MAX(salary),0) "Maximum",
    ROUND(MIN(salary),0) "Minimum",
    ROUND(SUM(salary),0) Sum, 
    ROUND(AVG(salary),0) -- you need no aliases here
    into vCount,
         vMax,
         vMin,
         vSum,
         vAvg
    FROM employees;
    --
    dbms_output.put_line('Count: ' || vCount || ' - ' || 
                            'Max: ' || vMax || ' - ' ||
                            'Min: ' || vMin || ' - ' ||
                            'Sum: ' || vSum || ' - ' ||
                            'Avg: ' || vAvg);
end;

Answer 2

这个问题不是 100% 明确的，但是您说您需要按公司进行，并且您还需要每个公司的员工人数？我猜你的表包含一个像 nCompanyID 这样的字段？

然后你会有：

SELECT
    nCompanyID as Company -- I don't know if you have an ID or a string for it...
    COUNT(*) as nbEmployees,
    ROUND(MAX(salary),0) as MaximumSalary,
    ROUND(MIN(salary),0) as MinimumSalary,
    ROUND(SUM(salary),0) as TotalSalary,
    ROUND(AVG(salary),0) as AverageSalary
FROM employees
GROUP BY nCompanyID;

请注意，这是在 MS SQL Server 中，但我确信 oracle 的 SQL 对于此类事情具有几乎相同的语法。