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1显示所有员工的姓名，部门号和部门名称 SELECT last_name,e.department_id,department_name from employees e LEFT JOIN dep...0113 -
七、聚合函数 1.常见的聚合函数 1. AVG / SUM AVG 求平均数 SELECT AVG (salary) FROM employees; 以下两个是字符串， 它们在求平均数和求和时...0136
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SELECT last_name,e.department_id,department_name from employees e LEFT JOIN departments d on e.depar...0190 -
SELECT last_name,e.department_id, department_name FROM employees e LEFT OUTER JOIN departments d ON ...0168
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1.avg/sum:只适用于数值类型的字段或变量 SELECT AVG(salary),SUM(salary) from employees; 字符串求和没有任何意义 SELECT AVG(last_...0184
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练习SELECT e.last_name,d.department_id,d.department_name FROM employees e,departments d WHERE e.depart...0124
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满外连接(mysql不支持使用FULL OUTER JOIN) SELECT employees_id,department_name FROM employees e FULL OUTER JOIN...1132
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SELECT employees_id,department_name FROM employees e 满外连接 SELECT EMPLOYEE_id,department_name FROM em...2129
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满外链接 MYSQL不支持FULL OUTER JOIN 做满外链接 SELECT employee_id,department_name FROM employees e FULL OUTER ...0128
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满外查询 错误写法(MySQL不支持FULL OUTER JOIN 做满外查询 ) SELECT employee_id,department_name FROM employees e FULL...0113
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select 122106; Mysql 不支持full outer join 做满外查询 select employee_id,department_name from employees e fu...0122
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满外连接 MySQL不支持FULL OUTER JOIN 做满外查询 SELECT employee_id,department_name FROM employees e FULL OUTER j...0125
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（一）SELECT last_name, e.department_id, department_name FROM employees e LEFT OUTER JOIN departments d...0738
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