sql-server - T-SQL 将行连接成字符串

Question

我试图在 select 语句上使用子查询来获取字段值，但我似乎无法找出正确的语法。我想提取公司名称列表，并作为该查询的字段，我想选择该公司的所有员工。

关于我做错了什么有什么想法吗？我得到的错误是

Only one expression can be specified in the select list when the subquery is not introduced with EXISTS

T-SQL 代码:

SELECT 
   company_name, 
   company_type, 
   (SELECT 
        employee_firstname, employee_lastname 
    FROM 
        tblemployees 
    WHERE 
        tblemployees.company_id = tblCompanies.company_id) as employees 
FROM 
    tblCompanies

期望的输出:

Company Name |  Company Type  | Employees
----------------------------------------------------------
Test Co      |  Construction  | Bob Smith, Jack Smith, etc

Answer 1

您需要使用 FOR XML PATH 或类似的解决方案连接名字和姓氏。有关各种方法的更多详细信息here .

SELECT DISTINCT
   c1.company_name, 
   c1.company_type,
   STUFF((SELECT
              ', ' + c2.employee_firstname + ' ' + c2.employee_lastname
          FROM
              tblCompanies c2
          WHERE
              c1.company_id = c2.company_id
          ORDER BY
              employee_lastname, employee_firstname
          FOR XML PATH(''), TYPE).value('.', 'varchar(max)'), 1, 1, '')
FROM tblCompanies c1

SQL Fiddle