SELECT * FROM employee WHERE (department, salary) IN ( SELECT department, MAX(salary) FROM employee GROUP BY department ) ORDER BY department; 使用窗口函数 row_number() WITH ranked_employees AS ( SELECT ROW_NUMBER() OVER ( PARTITION BY department ORDER BY salary DESC ) AS rn, * FROM empl...
GROUP BY语句通常与集合函数(COUNT,MAX,MIN,SUM,AVG)一起使用,以按一个或多个列对结果集进行分组。 SELECT column_name(s) FROM table_name WHERE condition GROUP BY column_name(s) ORDER BY column_name(s); 1. 2. 3. 4. 5. HAVING 子句 HAVING 子句 常常用在GROUP BY 之后 用来过滤分组,因为WHER...
column “class” must appear in the GROUP BY clause or be used in an aggregate function 就是说这个 select class是非法的。 刚从MySQL切到PostgreSQL后很可能会比较难受这个点。 其实有一种很简单的方法, 那就是你反正其他的字段其实都一样,随便取一个就行,所以还是保持原来的GROUP BY 子句,然后直接给所...
SELECT AVG(salary),job_id FROM employees GROUP BY job_id; #案例2:查询每个位置的部门个数 SELECT COUNT(*) AS 部门个数,location_id FROM departments GROUP BY location_id; 1. 2. 3. 4. 5. 6. 7. 8. 9. 2、可以实现分组前的筛选 ...
在使用Group-by的Select语句时,如果需要忽略PostgreSQL上的列,可以使用HAVING子句来实现。 HAVING子句是在GROUP BY子句之后使用的,用于过滤分组后的结果集。它可以包含聚合函数和条件表达式,用于筛选满足特定条件的分组。 以下是一个示例的Group-by的Select语句,忽略PostgreSQL上的列: ...
AS names(first, last) 表函数 表函数是产生一组行的函数,由基本数据类型(标量类型)或复合数据类型(表行)组成。它们在查询的 FROM 子句中用作表、视图或子查询。表函数返回的列可以包含在 SELECT、JOIN 或 WHERE 子句中,其方式与表、视图或子查询的列相同。
[ GROUP BY grouping_element [, ...] ] [ HAVING condition [, ...] ] [ WINDOW window_name AS ( window_definition ) [, ...] ] [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ] [ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS { FIRST | LAST } ...
create tablet1(id1 int,id2varchar(64));insert into t1values(1,’nanjing’),(1,’suzhou’),(2,’xingtai’),(2,’shijiazhuang’);select id1,string_agg(id2,’,’)group by id1;id1|string_agg---1|nanjing,suzhou2|xingtai,shijiazhuang array_agg函数和string_agg函数类似,最主要的区别为返回...
GROUP BY和HAVING子句 在通过了WHERE过滤器之后,生成的输入表可以使用GROUP BY子句进行分组,然后用HAVING子句删除一些分组行。 SELECT select_list FROM ... [WHERE ...] GROUP BY grouping_column_reference [, grouping_column_reference]... GROUP BY子句被用来把表中在所列出的列上具有相同值的行分组在一起。
第一种最直观的写法 SELECT*FROM employee WHERE(department,salary)IN(SELECT department,MAX(salary)FROM employee GROUP BY department)ORDER BY department; 使用窗口函数 row_number() WITHranked_employeesAS(SELECTROW_NUMBER()OVER(PARTITIONBYdepartmentORDERBYsalaryDESC)ASrn,*FROMemployee)SELECT*FROMranked_emplo...